What weakens your immune system?

9 Surprising Ways You’re Weakening Your Immune System

It should come as no surprise that washing your hands often, being fully vaccinated, getting enough sleep, and eating a healthy diet are effective ways of protecting yourself against viruses and other germs. What you may not realize is that other factors in your life could be compromising your body’s ability to protect itself.

How you spend your free time, your level of stress, how often you drink, how much physical activity you get, and even the air you breathe can take a toll on your immune system.


Prolonged periods of intense stress can affect the immune system, according to the National Cancer Institute. Stress makes the brain boost production of the hormone cortisol, which impairs the function of infection-fighting T cells, explains John Spangler, MD, a professor of family and community medicine at Wake Forest Baptist Medical Center in North Carolina.

Getting support from friends, setting priorities, exercising regularly, and practicing relaxation techniques like yoga and tai chi can help ease stress, says the National Institute of Mental Health (NIMH).


Feeling lonely could impair your immune system, according to a study published in the Journal of Neuroimmunology in December 2014. The research, done on rats, found that increased anxiety associated with loneliness leads to greater suppression of the immune system and more oxidative stress, or damage caused by free radicals. Research published in Psychological Science in February 2015 suggests that simply hugging someone can have a stress-buffering effect and reduce susceptibility to illness.

Sedentary Lifestyle

Over time, too much sitting and avoiding exercise can affect your body’s ability to fight infection, according to a January 2012 study in the American Journal of Preventive Medicine. Regardless of age, gender, and other harmful habits like smoking and drinking, a sedentary lifestyle is tied to an increased risk for premature death. Eventually, inactivity can lead to an impaired immune system, inflammation, and other chronic diseases, the study warns. Scheduling 30 minutes of regular exercise into your daily routine can help, the NIMH advises.

Too Much Exercise

Being a couch potato impairs your immune system, but the opposite extreme can also take a toll. Too much strenuous exercise, called overtraining syndrome, can be debilitating for the body and make it more vulnerable to infection, according to a December 2012 review in Acta Clinica Croatica. But a 2014 study suggests that regular, moderate physical activity can make you less susceptible to viruses.


Whether you’re smoking traditional cigarettes or e-cigarettes, you’re still being exposed to nicotine, which can have harmful effects on your immune system. Nicotine increases cortisol levels, while reducing B cell antibody formation and T cells’ response to antigens, explains Dr. Spangler. Vapor from e-cigarettes could damage the lungs and make them more susceptible to infection, according to the results of a study on mice published in PLOS One in February 2015. The researchers cautioned that e-cigarettes are unsafe because their vapor contains free radicals that can cause airway inflammation and impaired responses to bacteria and viruses.

Ultraviolet Radiation

Rising levels of certain air pollutants are depleting the ozone layer, increasing the level of harmful ultraviolet (UV) radiation from the sun. This could lead to higher rates of skin cancer, cataracts, and weakened immune systems, according to the Environmental Protection Agency (EPA). Exposure to environmental UV rays could also affect the cells responsible for triggering immune responses, increasing the risk of infection and possibly lowering defenses against skin cancer, the World Health Organization cautions. Wearing sunglasses, protective clothing, and sunscreen of SPF 30 or higher can help, the EPA advises.


A diet high in saturated fat impairs the immune system, and salt and sugar might also have negative effects, according to a June 2014 review published in Nutrition Journal. Obesity affects the immune system by reducing the number and function of white blood cells needed to fight infection, according to a May 2012 review in Proceedings of the Nutrition Society. The American Academy of Nutrition and Dietetics stresses that good nutrition is essential for a healthy immune system.


Even one bout of excessive drinking can reduce the immune system’s response to invading pathogens, Spangler says. “Alcohol’s major metabolite, acetaldehyde, likely impairs ciliary function in the lungs, making them more prone to bacterial and viral invasion,” he explains. Alcohol also impairs the process of attacking and breaking down bacteria and viruses, he says, and that puts people who abuse alcohol at higher risk for infection.


A sudden or tragic event can weaken your body’s immune response, according to the NIMH. Losing a loved one, for example, can boost production of nerve chemicals and hormones that increase your risk for more frequent and severe viral infections, such as the flu, the agency says. Bereavement is associated with increased cortisol response and immune imbalance, according to a June 2012 review published in Dialogues in Clinical NeuroSciences. Certain vaccines, including the flu shot, may be less effective for those coping with profound loss, according to the NIMH.

Your immune system is a fascinating, interconnected network. It protects you from millions of harmful bacteria, microbes, viruses, toxins and parasites, yet most people often don’t give it a second thought.

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At the break of skin and the openings of your mouth and nose, it is the border patrol. If invaders do get inside your body, it sends out lines of defense, whether in the blood, organs, muscles or bones.

This internal police force is vital to life, though sometimes it does get overzealous. When this happens, the immune system can work against us, causing allergic reactions or at its worst, autoimmune disorders, such as lupus and multiple sclerosis.

At other times, it weakens, fails and becomes ineffective.

Why does this happen? What turns the volume of your immune system up or down?

Rheumatologist Leonard Calabrese, DO, answers common questions about what happens when your immune system falters.

Q: What happens when your immune system fails?

A: Think of how many times you come into contact with someone who has a cold or the flu. Imagine how often your immune system fights off those germs and keeps you in the pink. But what if, instead, every one of those illnesses gained a foothold in your body? You might go from one illness to another, without ever recovering in between.

When the failure is severe, you will see more complications from those illnesses and infections, and you’ll recover much more slowly. Instead of bouncing back within days or a week, you could suffer for several weeks or months.

When your immune system fails completely, you’re left without any natural protection against illness. This leaves you open to “opportunistic infections” — sicknesses that can even come from things that ordinarily wouldn’t harm you. These can include recurrent pneumonia, herpes simplex and tuberculosis among other infections.

People who are immunocompromised, such as those with HIV, fall into this last group. This makes certain types of cancer, such as lymphoma, more likely.

Q: What happens with an overactive immune system?

A: In many cases, an immune system that overreacts is as harmful and dangerous as one that stops working.

In general, an overactive immune system leads to many autoimmune disorders — because of hyperactive immune responses your body can’t tell the difference between your healthy, normal cells and invaders. In essence, your immune system turns against you.

Q: What conditions can arise from an overactive immune system?

A: Common conditions caused by an overactive immune system include:

  • Rheumatoid arthritis: Your immune system attacks your joints, leading to inflammation, redness, pain and stiffness. Over time, your joints can become deformed and you can lose function.
  • Multiple sclerosis: Your immune system destroys the fatty layer that surrounds and protects your nerves from damage. Without it, you’re vulnerable. As this disease progresses, it attacks your brain, spine and eyes, causing problems with your balance, muscle control, vision and other bodily functions.
  • Celiac disease: With this condition, when you eat gluten your immune system attacks the small intestines, damaging the finger-like projections (called villi) that help your body absorb nutrients.

Other autoimmune conditions include:

  • Lupus (affects skin, joints and blood cells)
  • Vasculitis (affects blood vessels)
  • Sjögren’s syndrome (causes dry eyes and dry mouth)
  • Inflammatory bowel syndrome (affects the digestive tract)
  • Chronic fatigue syndrome (causes sleep abnormalities and pain)

Q: What causes immune system failure?

A: Doctors still don’t know exactly why the immune system sometimes fails. But, there are clues to how it happens. The immune system is an integrated network that’s hard-wired into your central nervous system, Dr. Calabrese says. So, when it’s healthy, everything works automatically.

But, things go haywire when the system starts to crumble. For example, if you don’t sleep well and get stressed out, your body will produce more of the stress hormone cortisol.

Over time, high cortisol levels can have a degenerative effect on your body. Healthy bone and muscle break down and slow the healing process. Cortisol can interfere with digestion and metabolism, as well as adversely affecting your mental functions.

Q: How can you help your immune system?

A: Though we don’t always know exactly why an immune system fails, we do know that adopting healthy habits can help keep your immune system ticking along well and always ready for defensive action, Dr. Calabrese says.

A healthy diet, regular exercise, getting enough sleep and managing stress all can help. These steps help support good cardiovascular health, which, in turn, contributes to a healthy immune system.

Five Factors that Affect the Immune System

The immune system is influenced by the sleep-wake cycles of our circadian rhythms. Studies suggest that while we’re sleeping we have decreased levels of the stress hormone cortisol, which can suppress immune function, and increased signals that activate the immune system. 4 Even though we know that sleep is important, it can be difficult to get enough, especially during busy times of the year. According to a Gallup survey, 56% of adults say they get enough sleep. However, 7 hours is the minimum recommended amount of sleep for adults and only 40% of us are averaging 6.8 hours of sleep per night. 3

3. Nutrients From Food

Everywhere we turn, we see PSAs, news stories and blogs boasting the importance of fruits and vegetables for a plethora of health reasons, and the same applies to immune health. Studies show vitamins C, A, E, B6 and B12 and minerals like iron and zinc are important for the maintenance of immune function, all of which can be found in fruits and veggies. 7 If you’re a clean-eating enthusiast, you’re probably getting enough of these vitamins and minerals, but many of us aren’t. The Dietary Guidelines for Americans recommends 4.5 cups of fruit and vegetables per day. 5

4. Cortisol Levels

Another challenge that plagues our immune system is a familiar foe to many of us. STRESS. Hectic work schedules and abundant daily responsibilities can leave us frazzled. Increased levels of the stress hormone, cortisol, makes it difficult for the immune system to function properly. The American Psychological Association reports that 75% of Americans experience moderate to high levels of stress. 8,9 In addition to the direct impact of stress on immune function, unmanaged stress can influence our sleep patterns, our mood, our dietary intake and our physical activity levels. All of these factors are associated with immune system function 8

5. Supplement Intake

To promote and support healthy behaviors, supplements and fortified foods have been widely used to support immune health. According to Nutraingredients, 29% of supplement users take an immune health product. 11

Beta-glucan is an emerging ingredient in immune health supplements. Beta-glucan is a naturally occurring glucose polymer or insoluble fiber found in cereal grains like oat and barley, certain types of mushrooms, yeast, seaweed, and algae. Although all types of beta-glucan have some health benefit, the beta-glucan found in yeast, mushrooms and algae can provide benefits that support immune health. 10 Kemin has recently launched a new line of beta-glucan ingredients sourced from a proprietary strain of algae.

BetaVia™ Beta-glucan for Immune Support

BetaVia Complete and BetaVia Pure are beta-glucan ingredients naturally-sourced from Euglena gracilis (algae). In vitro and animal studies show that BetaVia ingredients can prime key immune cells, thereby strengthening the body’s immune defenses. Algae-sourced BetaVia ingredients are distinct from currently available beta-glucan ingredients that are derived from yeast or mushrooms. True to our commitment to providing science-backed ingredients, Kemin has an ongoing BetaVia research program focused on discovery and innovation to bring cutting-edge science, insights and claims to our customers.

Stress Weakens the Immune System

Stressed out? Lonely or depressed? Don’t be surprised if you come down with something. Psychologists in the field of “psychoneuroimmunology” have shown that state of mind affects one’s state of health.

In the early 1980s, psychologist Janice Kiecolt-Glaser, PhD, and immunologist Ronald Glaser, PhD, of the Ohio State University College of Medicine, were intrigued by animal studies that linked stress and infection. From 1982 through 1992, these pioneer researchers studied medical students. Among other things, they found that the students’ immunity went down every year under the simple stress of the three-day exam period. Test takers had fewer natural killer cells, which fight tumors and viral infections. They almost stopped producing immunity-boosting gamma interferon and infection-fighting T-cells responded only weakly to test-tube stimulation.

Those findings opened the floodgates of research. By 2004, Suzanne Segerstrom, PhD, of the University of Kentucky, and Gregory Miller, PhD, of the University of British Columbia, had nearly 300 studies on stress and health to review. Their meta-analysis discerned intriguing patterns. Lab studies that stressed people for a few minutes found a burst of one type of “first responder” activity mixed with other signs of weakening. For stress of any significant duration – from a few days to a few months or years, as happens in real life – all aspects of immunity went downhill. Thus long-term or chronic stress, through too much wear and tear, can ravage the immune system.

The meta-analysis also revealed that people who are older or already sick are more prone to stress-related immune changes. For example, a 2002 study by Lyanne McGuire, PhD, of John Hopkins School of Medicine with Kiecolt-Glaser and Glaser reported that even chronic, sub-clinical mild depression may suppress an older person’s immune system. Participants in the study were in their early 70s and caring for someone with Alzheimer’s disease. Those with chronic mild depression had weaker lymphocyte-T cell responses to two mitogens, which model how the body responds to viruses and bacteria. The immune response was down even 18 months later, and immunity declined with age. In line with the 2004 meta-analysis, it appeared that the key immune factor was duration, not severity, of depression. And in the case of the older caregivers, their depression and age meant a double-whammy for immunity.

The researchers noted that lack of social support has been reported in the research as a risk factor for depression, an insight amplified in a 2005 study of college students. Health psychologists Sarah Pressman, PhD, Sheldon Cohen, PhD, and fellow researchers at Carnegie Mellon University’s Laboratory for the Study of Stress, Immunity and Disease, found that social isolation and feelings of loneliness each independently weakened first-year students’ immunity.

In the study, students got flu shots at the university health center, described their social networks, and kept track of their day-to-day feelings using a handheld computer (a new technique called “momentary ecological awareness”). They also provided saliva samples for measuring levels of the stress hormone cortisol. Small networks and loneliness each independently weakened immunity to a core vaccine component. Immune response was most weakened by the combination of loneliness and small social networks, an obvious health stress facing shy new students who have yet to build their friendship circles.

Although you may not be able to fully prevent a cold or flu this season, a healthy immune system is one way to give your body extra protection. Focusing on nutrient-rich foods and healthy lifestyle behaviors can help you and your family stay a step ahead of germs this season.

Immune-Boosting Nutrients

The following nutrients play a role in the immune system and can be found in a variety of foods:

  • Beta Carotene is found in plant foods, such as sweet potatoes, spinach, carrots, mango, broccoli and tomatoes.
  • Vitamin C-rich foods include citrus fruits, berries, melons, tomatoes, bell peppers and broccoli.
  • Vitamin D is found in fatty fish and eggs. Milk and 100% juices that are fortified with vitamin D also are sources of this important nutrient.
  • Zinc tends to be better absorbed from animal sources such as beef and seafood, but also is in vegetarian sources such as wheat germ, beans, nuts and tofu.
  • Probiotics are “good” bacteria that promote health. They can be found in cultured dairy products such as yogurt and in fermented foods such as kimchi.
  • Protein comes from both animal and plant-based sources, such as milk, yogurt, eggs, beef, chicken, seafood, nuts, seeds, beans and lentils.

Focus on Balance

To help keep your immune system healthy all year long, focus on a balanced eating plan, adequate sleep and stress management.

Aim for five to seven servings of vegetables and fruits daily to get immune-boosting vitamins, minerals and antioxidants.

Good hygiene and hand-washing help prevent the spread of germs. Remember to wash produce before eating or using in recipes. Clean glasses, forks, spoons and other utensils to reduce the spread and growth of bacteria.

Find healthy and appropriate ways to cope with stress, such as meditation, listening to music or writing. Physical activity also is a great way to help manage stress and may help reduce the risk of some chronic diseases that could weaken your immune system further.

Lack of sleep contributes to a variety of health concerns, such as a weakened immune system. Seven to nine hours is recommended each day for adults, and children need eight to 14 hours, depending on their age.

What About Herbals?

Many herbal remedies are marketed to help fight colds or shorten their duration but check with your health care provider before taking any supplements or medications.

Aging changes in immunity

Your immune system helps protect your body from foreign or harmful substances. Examples are bacteria, viruses, toxins, cancer cells, and blood or tissues from another person. The immune system makes cells and antibodies that destroy these harmful substances.


As you grow older, your immune system does not work as well. The following immune system changes may occur:

  • The immune system becomes slower to respond. This increases your risk of getting sick. Flu shots or other vaccines may not work as well or protect you for as long as expected.
  • An autoimmune disorder may develop. This is a disease in which the immune system mistakenly attacks and destroys healthy body tissues.
  • Your body may heal more slowly. There are fewer immune cells in the body to bring about healing.
  • The immune system’s ability to detect and correct cell defects also declines. This can result in an increased risk of cancer.


To decrease the risks from immune system aging:

  • Get the flu and pneumonia vaccines, and any other vaccines your health care provider recommends.
  • Get plenty of exercise. Exercise helps boost your immune system.
  • Eat healthy foods. Good nutrition keeps your immune system strong.
  • DO NOT smoke. Smoking weakens your immune system.
  • Limit your intake of alcohol. Ask your provider how much alcohol is safe for you.
  • Look into safety measures to prevent falls and injuries. A weak immune system can slow healing.


As you grow older, you will have other changes, including in your:

  • Hormone production
  • Organs, tissues, and cells

The negative effects of smoking are well documented, with medical researchers all agreeing that tobacco products are bad news when it comes to overall health. Heart disease, lung cancer, COPD, stroke – these are just a few of the conditions linked to tobacco use.

There are other health consequences to smoking that you may not equate with using tobacco products. While having a heart attack or being diagnosed with lung cancer are obvious consequences of smoking that would immediately get your attention, there are more subtle health issues that may already be manifesting themselves in your everyday life.

Smoking and the Immune System

That cold you just can’t seem to shake might actually be hanging around due to your smoking habit. Not only does smoking cause serious health conditions like cancer, but it also lessens your body’s immune response, making you more susceptible to infections. You may also find it harder to shake everyday illnesses that are no big deal to most healthy adults. Tobacco products damage virtually every system of the body, and the immune system is no different.

Ways Smoking Affects the Immune System

Smoking may negatively affect the immune system in a variety of ways:

Higher risk of respiratory infections

It’s no surprise that smoking increases one’s risk of developing respiratory illnesses, such as bronchitis or pneumonia, according to Better Health Channel. This is due to tobacco smoke’s immune suppressing effects, as well as smoke entering and damaging delicate lung tissues.

More frequent infections and prolonged illness

Smoking damages and destroys antibodies in the blood stream. Antibodies normally help fight off infectious illnesses, but since smokers have fewer of these antibodies available, they may experience more severe infections and they may remain sick longer than non-smokers. Wounds and sports-related injuries also take longer to heal for smokers than for non-smokers.

Fewer available antioxidants

Smoking destroys antioxidants in the body, such as vitamin C. Antioxidants help kill free radicals, or cells responsible for causing cancer.


According to Livestrong, and the University of Cincinnati, smoking not only weakens immune response when it comes to fighting off infections. It may also turn the immune system against the body’s own cells. Some smokers which experience severe or chronic lung disease may be suffering from an autoimmune response, meaning their immune systems are attacking lung tissue.


Preventing Immune System Disorders

Despite the risks, there are things smokers can do to reduce the risk of these negative outcomes.

Eat right

Eating a healthy diet to replenish lost vitamins and minerals may help keep you healthy


Exercising improves oxygenation of the bloodstream and benefits cardiovascular function, both of which keep the immune system stronger

Get outdoors

Vitamin D helps boost immune function, and getting 10 to 15 minutes of sunlight per day helps the body create its own stores of this vitamin.


In some cases, supplementation with vitamin C and other immune boosting vitamins may be beneficial.

Avoid exposures

Stay away from areas where infectious disease are known to spread as much as possible, especially during outbreaks. If you know someone who has been sick, avoid that person until they are no longer contagious if possible.


This is the best way to improve immune function. Quitting is now more possible than ever with smoking cessation aids being available to those who want to stop smoking for good. Luckily, the body’s immune function will begin to improve right away after quitting.

For most of us, stress is just a part of life. It can last for a few hours — like the time leading up to a final exam — or for years — like when you’re taking care of an ailing loved one.

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Stress is sometimes a motivator that helps you rise to the occasion. At other times, it’s simply overwhelming. Whatever the case, if it’s chronic, it can take a toll on your immune system.

Clinical immunologist Leonard Calabrese, DO, offers insights on how stress impacts your immunity and what you can do to minimize the effect.

“Eliminating or modifying these factors in one’s life is vital to protect and augment the immune response,” he says. “It’s necessary to buffer the inevitability of the aging process.”

What impact does stress have on you?

Stress occurs when life events surpass your abilities to cope. It causes your body to produce greater levels of the stress hormone cortisol.

In short spurts, cortisol can boost your immunity by limiting inflammation. But over time, your body can get used to having too much cortisol in your blood. And this opens the door for more inflammation, Dr. Calabrese says.

In addition, stress decreases the body’s lymphocytes — the white blood cells that help fight off infection. The lower your lymphocyte level, the more at risk you are for viruses, including the common cold and cold sores.

High stress levels also can cause depression and anxiety, again leading to higher levels of inflammation. In the long-term, sustained, high levels of inflammation point to an overworked, over-tired immune system that can’t properly protect you.

Conditions that stress causes

If you don’t control high stress levels, chronic inflammation can accompany it and can contribute to the development and progression of many diseases of the immune system such as:

  • Arthritis
  • Fibromyalgia
  • Lupus
  • Psoriasis
  • Inflammatory bowel disease

Under sustained, long-term stress, you also can develop cardiovascular problems, including a fast heart rate and heart disease, as well as gastric ulcers. You’ll also be at greater risk for type 2 diabetes, various cancers and mental decline.

How can you better manage your stress levels?

Stress reduction strategies not only give your mind a break, but they can also relieve the pressure on your immune system. You can take steps to reduce short-term and long-term stress, Dr. Calabrese says. Two tactics are most effective:

  1. Meditation (also called mindfulness): Meditate for 10 minutes to 15 minutes three or four times weekly to lower your stress. It reduces your cortisol levels and reduces inflammation. Research also shows it helps prevent the breakdown of your chromosomes that leads to cancer and premature aging.
  2. Yoga: Practicing yoga also lowers stress hormone levels and calms your nervous system to reduce inflammation. Deep breathing helps boost your resistance to infection. Inverted poses in yoga help circulate fluid through your lymphatic system, filtering out toxins.

Stress in acute situations, however, can be healthful and protective, so it’s not all bad for us. Remember: it’s chronic stress that we seek to control.

How Drug Abuse Can Weaken or Suppress the Immune System

When a person struggles with substance abuse or addiction, they may experience several side effects from chronically ingesting these substances. Long-term struggles with alcohol or drugs can lead to considerable damage to many systems in the body, especially the immune system. The immune system may be harmed directly by intoxicating substances, or the way the drug is ingested may contribute to a higher risk of infection, coupled with a lower immune response.

Even if someone who suffers from addiction does not develop more serious problems, like cognitive problems, heart disease, lung disease, or liver failure, harm done to the immune system can lead to serious, recurring, or incurable infections. Some of these infections may cause other long-term problems, or lead to death.

Substance Abuse and the Immune System

Some of the addictive substances that can damage the immune system and lead to infectious diseases are described in further detail below.

  • Alcohol: Decreased liver and pancreas functioning can lead to immune system problems. Chronic alcohol abuse and pneumonia are linked. Reduced inhibitions associated with alcohol consumption can also lead to sexually transmitted infections, especially HIV or HSV-2, which can suppress the immune system and cause the body to become more susceptible to other infections.
  • Cocaine: Snorting cocaine damages mucous membranes in the nose, throat, and lungs, which in turn can lead to upper respiratory infections or a susceptibility to these conditions. Smoking crack cocaine also damages the lungs and can reduce the immune system’s response to lung infections like bronchitis or pneumonia.
  • Marijuana: This intoxicating drug affects several kinds of cells in the body, which can ultimately harm the immune system. Smoking marijuana reduces the body’s ability to resist infections from viruses, bacteria, fungi, and protozoa. It can also increase the risk of developing cancer. One study found that marijuana directly affects a type of cell called myeloid-derived suppressor cells, which suppress the immune system’s response in certain situations. By enhancing the effect of these suppressor cells, marijuana suppresses the immune system in general, leading to a higher risk of cancer or infections in people who struggle with marijuana addiction.
  • Nicotine: As with marijuana and crack cocaine, smoking cigarettes can lead to upper respiratory problems and a lowered immune system response to infections in that area.
  • Opioids: This class of drugs includes heroin, morphine, fentanyl, opium, and prescription painkillers. While all narcotics have some effect on the immune system, injecting drugs into the veins increases the risk of viral infections like HIV and hepatitis B or C (due to sharing needles) and bacterial or fungal infections. This is especially dangerous in people whose immune systems are already compromised. Crushing and snorting narcotic drugs can also increase the risk of upper respiratory infections due to damage to the mucous membranes in the nose, throat, and upper lungs. Morphine and related opioids have been found to directly impact white blood cells, which can reduce the ability of the immune system to react to diseases.

Overcome Addiction to Help the Immune System Heal

Entering a rehabilitation program to overcome addiction can help the body heal. Medical professionals can treat infections like pneumonia, STIs, or other diseases. Conditions like HSV or HIV that are incurable can also be treated, allowing the person to live for extended periods of time without further harm from the disease. Some harm done to the immune system or other body systems may be reversed when the person becomes sober, so prompt treatment is key.

Disorders of the Immune System

Your immune system is your body’s defense against infections and other harmful invaders. Without it, you would constantly get sick from bacteria or viruses.

Your immune system is made up of special cells, tissues, and organs that work together to protect you.

The lymph, or lymphatic, system is a major part of the immune system. It’s a network of lymph nodes and vessels. Lymphatic vessels are thin tubes that branch, like blood vessels, throughout the body. They carry a clear fluid called lymph. Lymph contains tissue fluid, waste products, and immune system cells. Lymph nodes are small, bean-shaped clumps of immune system cells that are connected by lymphatic vessels. They contain white blood cells that trap viruses, bacteria, and other invaders, including cancer cells.

White blood cells are the cells of the immune system. They are made in one of your lymph organs, the bone marrow. Other lymph organs include the spleen and thymus.

What can go wrong with your immune system?

When your immune system doesn’t work the way it should, it is called an immune system disorder. You may:

  • Be born with a weak immune system. This is called primary immune deficiency.

  • Get a disease that weakens your immune system. This is called acquired immune deficiency.

  • Have an immune system that is too active. This may happen with an allergic reaction.

  • Have an immune system that turns against you. This is called autoimmune disease.

Immune system disorders

Here are some common examples:

  • Severe combined immunodeficiency (SCID). This is an example of an immune deficiency that is present at birth. Children are in constant danger of infections from bacteria, viruses, and fungi. This disorder is sometimes called “bubble boy disease.” In the 1970s, a boy had to live in a sterile environment inside a plastic bubble. Children with SCID are missing important white blood cells.

  • Temporary acquired immune deficiencies. Your immune system can be weakened by certain medicines, for example. This can happen to people on chemotherapy or other drugs used to treat cancer. It can also happen to people following organ transplants who take medicine to prevent organ rejection. Also, infections like the flu virus, mono (mononucleosis), and measles can weaken the immune system for a brief time. Your immune system can also be weakened by smoking, alcohol, and poor nutrition.

  • AIDS. HIV, which causes AIDS, is an acquired viral infection that destroys important white blood cells and weakens the immune system. People with HIV/AIDS become seriously ill with infections that most people can fight off. These infections are called “opportunistic infections” because they take advantage of weak immune systems.

An overactive immune system

If you are born with certain genes, your immune system may react to substances in the environment that are normally harmless. These substances are called allergens. Having an allergic reaction is the most common example of an overactive immune system. Dust, mold, pollen, and foods are examples of allergens.

Some conditions caused by an overactive immune system are:

  • Asthma. The response in your lungs can cause coughing, wheezing, and trouble breathing. Asthma can be triggered by common allergens like dust or pollen or by an irritant like tobacco smoke.

  • Eczema. An allergen causes an itchy rash known as atopic dermatitis.

  • Allergic rhinitis. Sneezing, a runny nose, sniffling, and swelling of your nasal passages from indoor allergens like dust and pets or outdoor allergens like pollens or molds.

Autoimmune disease

In autoimmune diseases, the body attacks normal, healthy tissues. The cause is unknown. It is probably a combination of a person’s genes and something in the environment that triggers those genes.

Three common autoimmune diseases are:

  • Type 1 diabetes. The immune system attacks the cells in the pancreas that make insulin. Insulin removes sugar from the blood to use as energy.

  • Rheumatoid arthritis. This type of arthritis causes swelling and deformities of the joints. An auto-antibody called rheumatoid factor is in the blood of some people with rheumatoid arthritis.

  • Lupus. This disease that attacks body tissues, including the lungs, kidneys, and skin. Many types of auto-antibodies are found in the blood of people with lupus.

No one knows exactly what causes autoimmune diseases, but many factors seem to be involved. If you have an immune system disorder, learn as much as you can about it. And work closely with your healthcare providers to manage it.

Before You Go

Make an appointment with a doctor at least a month before your trip to discuss vaccines, medications, and travel health advice.

No matter where you go, wash your hands often. Also, try to avoid touching surfaces that other people have touched, such as doorknobs and stair rails, with your bare hands.


Check CDC’s destination tool to see the vaccines recommended for your destination, and talk to your doctor about which are right for you.

If you have a weakened immune system, you can safely receive most vaccines recommended for travelers. However, the vaccines may be less effective than in people with fully healthy immune systems. Your doctor may recommend blood tests to confirm that a vaccine you received will provide you with adequate protection against disease, or suggest additional precautions to keep you safe.

Vaccines made from live viruses, such as MMR (measles, mumps, and rubella) and varicella, however, are not safe for many people with weakened immune systems. Talk to your doctor what your options are for protecting yourself against these diseases.

Yellow fever vaccine is another example of a vaccine made from a live virus. People whose immune systems are very weak, such as people with low T-cell counts due to HIV infection or people receiving cancer chemotherapy, should not receive yellow fever vaccine. If there is a risk of yellow fever at your destination, CDC recommends delaying your trip until your immune system is healthy enough for you to receive the vaccine. Some countries may require the vaccine, even if there is no risk of yellow fever. If that is the case, ask your doctor about a medical waiver for the vaccine.


Make sure your doctor knows about all the medicines you take regularly, including vitamin supplements, so that they can anticipate potential interactions.

You may need to take medicine to prevent malaria, depending on your destination. People with weakened immune systems can get seriously ill from malaria. It is important to follow closely your doctor’s instructions for taking the medicine, which may include taking it for several weeks before and after the trip. You should also take steps to avoid mosquito bites: wear insect repellent, wear long pants and sleeves, and sleep under a bed net if your rooms are open to the outdoors.

Depending on where you are going and what you will be doing, your doctor may also prescribe medicine to prevent altitude illness or to treat travelers’ diarrhea(/travel/page/travelers-diarrhea). People with weakened immune systems are especially prone to travelers’ diarrhea. Be sure to follow CDC’s advice for eating and drinking safely.

Overall, if you are feeling sick, do not travel before talking to your doctor.

More Information

Yellow Book: Immunocompromised Travelers

What Happens When the Immune System Does Not Work Properly?

When our immune system responds to something that is not an infectious agent, it can cause symptoms of disease unnecessarily. Allergic reactions are associated with this type of immune response. Likewise, sometimes our immune systems overreact, overwhelming our body and often resulting in death.

Allergies and allergic reactions

Allergic responses are most closely associated with a type of immune system cell, called a mast cell. Mast cells can be found in large numbers just beneath our skin and the linings of our respiratory, digestive, and genital tracts. Their main role is to protect us from parasites, but they are more “famous” for their role in allergic reactions. When a mast cell is activated — either by a parasite or in the case of allergic reactions, by a non-infectious agent perceived to be a pathogen — it releases a chemical called histamine. Histamine causes inflammation, recruits white blood cells to the area, increases mucus production and blood flow, and may also cause muscular contraction in an attempt to expel the pathogen. Mast cells that line the respiratory and digestive systems are responsible for muscle contractions that cause coughing, sneezing, vomiting and diarrhea. Mast cells not only require a pathogen, but they also rely on linkages with IgE or IgG antibodies to activate an immune response.

The type of allergic response generated is characterized by the type of antibody the mast cell is associated with when it is activated:

Immediate hypersensitivity reactions involve IgE antibodies

These are the more common type of allergic reaction, causing conditions such as:

  • Allergies to environmental agents (e.g., pollens), foods and medications
  • Eczema
  • Anaphylactic reactions

Symptoms can be minor nuisances or require emergency intervention, such as shots of epinephrine or emergency medical interventions.

People can develop these types of reactions as a result of genetic predisposition or environmental exposures early in life. Some people wonder if allergies are so common because children are not exposed to enough infectious agents early in life; this is known as the “hygiene hypothesis.” However, the environmentally based contributors to the development of immediate hypersensitivity appear to be multifactorial and complex. Respiratory and gastrointestinal infections, pollution, diet, and tobacco smoke have all been considered as potentially affecting the development of these types of reactions.

These types of reactions typically occur within 30 minutes of exposure to an allergen.

Hypersensitivity reactions involving IgG antibodies

Hypersensitivity reactions can also be caused by involvement of IgG antibodies with mast cells. Although these reactions are caused by a different part of the immune system, the symptoms an affected person experiences may be similar. This type of reaction can occur:

  • After taking certain kinds of medications, such as penicillin.
  • In response to the introduction of large amounts of airborne pathogens, such as molds or dust, such as from working on a farm. This condition is known as farmer’s lung.
  • As a result of chronic viral or bacterial infections, such as damage to the liver resulting from a long-term viral infection or to the heart following a long-term, undetected bacterial infection.

Historically, when treatment with antibody preparations made from horse serum were more common, people might also have reactions of this nature and develop an illness referred to as “serum sickness.” As technology has improved, this illness has become less common.

These types of reactions typically occur one to two weeks after exposure to an allergen.

Reactions involving T cells

Reactions that involve T cells tend to appear less rapidly than those caused by mast cell activation, occurring over days. These can include:

  • Delayed hypersensitivity reactions resulting from exposure to proteins in insect venom or from the bacteria that causes tuberculosis.
    Scientists and clinicians use the reaction to tuberculosis proteins as a way of monitoring for exposure to the bacteria. The tuberculin, or Mantoux, test involves putting a small amount of one of the proteins under the skin and watching over a period of two to three days to see if a reaction occurs.
  • Allergic contact dermatitis results from exposure to chemicals or agents that result in a T cell response right below the surface of the skin, such reactions to poison ivy or some small metals, such as nickel.

These types of reactions typically occur one to two weeks after exposure to an allergen.

Cytokine storm

Anytime our immune system responds to a potential infection, some damage to normal tissues also occurs. The innate immune response is non-specific and fast-acting resulting in tissue damage, and the adaptive immune system targets cells that show evidence of being infected. Most often this damage is relatively minimal and other components of the immune response work to “restore order” in the infected area even as the battle rages.

However, if the tissue damage is severe, some pathogens may get into the bloodstream and infect other parts of the body. When an infection reaches the bloodstream, a person is said to have sepsis. The result is that immune responses are occurring in battles throughout the body.

Sometimes, this attack — coupled with the immune response to it — can become overwhelming leading to what has been coined a “cytokine storm.” When this happens, the immune response essentially destroys the ability of the body to carry on normal function. A person’s organs begin to stop functioning, and medical care may or may not be successful in gaining control of the situation. Scientists do not completely understand why certain pathogens seem to be more likely to induce this kind of an immune response, nor do they understand why some infected people are more likely to succumb to this type of immune response. One example of a time when this occurred with greater frequency was during the 2009 H1N1 pandemic. While some people became ill and recovered; others died as a result of an overzealous immune response. By studying these types of occurrences, scientists hope to learn more about how and why they occur in order to better respond to and prevent them in the future.

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