Having an allergic reaction

When Is an Allergic Reaction an Emergency?

How to Identify Anaphylaxis

The signs and symptoms of anaphylaxis can vary greatly from person to person as well as from time to time in the same person. Also, they may develop very quickly — within seconds of exposure to an allergen — or evolve over an hour or so.

The most common signs and symptoms of an allergic reaction include:

  • Cough, difficulty or irregular breathing, wheezing, itchy throat or mouth, and difficulty swallowing
  • Nausea, vomiting, abdominal pain, and diarrhea
  • Itchiness, red bumps or welts on the skin (hives), and skin redness
  • Dizziness, lightheadedness, heart palpitations, chest discomfort or tightness, mental confusion, weakness, lower blood pressure, rapid pulse, loss of consciousness, and fainting

An allergic reaction becomes more serious and is considered a medical emergency when any of the signs or symptoms are particularly severe, such as loss of consciousness or difficulty breathing, or if different parts or systems of the body are involved, such as having the combination of hives and vomiting, Dr. Sicherer says.

How to Treat Anaphylaxis

As soon as anaphylaxis is detected, call 9-1-1 immediately and administer epinephrine if available. Try to keep the person as calm as possible.

If he or she has been diagnosed with a severe allergy, emergency medicine should be on hand. “The only treatment is injectable epinephrine,” says Robert Wood, MD, a professor of pediatrics and the chief of the division of pediatric allergy and immunology at Johns Hopkins Children’s Center in Baltimore, Md. “The most common misconception is that epinephrine is dangerous, which isn’t the case. Some doctors will often warn people not to give epinephrine until the last resort, but people with a severe allergic reaction need to take it sooner rather than later.”

People who have severe allergies may be told by their doctor to take a dose of epinephrine even before serious symptoms develop. “For example, if someone has a severe peanut allergy and they know they ate peanut, you could reasonably give the epinephrine before symptoms occur or if there were only mild ones,” Sicherer says.

While waiting for medical assistance to arrive, follow these potentially life-saving tips:

  • Avoid giving any oral allergy medicine and any liquids if the person is having trouble breathing.
  • If the allergic reaction is from a bee sting, scrape the stinger off with a credit card or fingernail. Do not use tweezers, which will release more venom into the sting site.
  • To help prevent shock, have the person lie flat with his or her feet elevated about 12 inches and cover him or her with a blanket or jacket. Do not put the person in this position if it causes discomfort or if a neck, back, or leg injury is suspected.
  • Do not put a pillow under the person’s head if he or she is having trouble breathing.

At the Emergency Room

Treating anaphylaxis doesn’t end with injecting epinephrine, even if the person feels better. The next step is seeking medical care at an emergency room (ER).

“The reason you must go to the ER is because you’re having a serious allergic reaction, and even if you feel better after taking epinephrine, the symptoms can still come back,” Sicherer says.

In fact, sometimes a person may get better after a severe allergic reaction but then have symptoms come back even stronger several hours later, which is called biphasic anaphylaxis, he adds. “You should go to the ER and stay there for at least four hours to make sure the symptoms are under control,” Sicherer says. Medical personnel will monitor you and give additional medications if needed.

Pollen, dust, animal dander, nuts, shellfish and other foods — these can all cause an allergic reaction in susceptible people.

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The symptoms range from being mildly uncomfortable and annoying to serious and life-threatening. So it’s good to know what to do if you or someone you’re with has an allergic reaction.

You may need to act quickly.

Here, allergist and immunologist Bela Faltay, MD, answers common questions about allergic reactions and how to handle them:

1. What happens during an allergic reaction?

When you eat, breathe in or touch something you’re allergic to, your immune system produces histamines to deal with the bothersome substance (allergen).

This immune response can cause several symptoms, including:

  • Itching
  • A rash
  • Hives (large, pink bumps or swollen areas)
  • Sneezing and watery eyes
  • Swelling in the mouth or throat
  • Rapid or difficult breathing

2. What should you do for throat swelling and difficulty breathing?

Call 911 immediately for medical help. Sometimes severe allergic reactions that cause you to struggle for breath can also create a sense of impending doom, says Dr. Faltay.

If the person who’s having an allergic reaction stops talking and simply stares, that’s a red flag as well.

“Calling 911 is better than driving to the emergency department,” he says. “Emergency medical technicians in an ambulance have protocols and access to treatments specifically for severe allergic reactions.”

3. What can you do to relieve itching, redness or a rash?

Wash the area with mild soap and lukewarm water. Apply hydrocortisone cream or lotion. Calamine lotion and cool compresses may also bring relief.

If you know what’s causing the reaction, stop using the product or wearing the item. Take off makeup or earrings if they’re the cause.

If you’re allergic to poison ivy, sumac or oak and have been exposed, wash clothing and other items that may have the irritant (an oily sap called urushiol) on them.

If your itchiness is severe, if your rash doesn’t go away, or if you see signs of infection, call your doctor.

4. What’s the best way to treat itching, sneezing and watery eyes?

When you have multiple allergic symptoms, an over-the-counter antihistamine such as loratadine (Claritin®) can treat them.

Dr. Faltay advises against using products that have a sedative effect, such as Benedryl®.

5. What should you do when hives develop?

The hives will subside in time. Meanwhile, it helps to apply cool compresses, to avoid hot showers and bath water, to wear loose clothing and to sleep in a cool room.

Be sure to work with your doctor to identify what’s triggering your hives.

6. Can allergies occur unexpectedly?

Yes. It’s important to know that some allergies are linked to others.

For example, if you’re allergic to latex, it’s possible that you’ll also react to avocados, kiwifruit and other tropical fruit. And if you’re allergic to birch pollen, it’s possible that you’ll react to apples or peaches as well.

It’s important to note that what seems like a food allergy can sometimes be food intolerance instead, notes Dr. Faltay.

7. What if you don’t know what’s causing your reaction?

Follow up with your doctor and ask about allergy testing, he advises. Testing can help pinpoint the cause of your reaction, and help you avoid triggers and future reactions.

Signs of a reaction

(Image credit: Markson Sparks/Richard Neely/REX/, File)

Dealing with allergies is tough. More than 50 million Americans have some type of allergy, according to the American College of Allergy, Asthma and Immunology. Most of the time, the body responds to outdoor and indoor allergens with mild reactions, such as a runny nose or sneezing. Sometimes, the reaction is more severe, such as stomach cramps, dizziness or difficulty breathing. But some people with allergies react in more unusual ways. Here are 7 particularly strange symptoms people have developed during an allergic reaction.

An odd, itchy rash

(Image credit: BSIP/UIG/Getty, File)

An 11-year-old boy developed an itchy rash on his abdomen and under his wristwatch a week after he was fitted for his braces, according to a 2004 case report published in the journal Dermatitis. It turned out, the boy was allergic to the nickel in the braces. The silver-colored metal is often mixed with other metals and is found in coins, jewelry eyeglass frames, key and home fixtures. Nickel is also the most common metal that people have allergic reactions to, and it’s known to cause a red, itchy, bumpy rash.

Skin tumors

(Image credit: Kirill Kukhmar/TASS/Getty)

Some people who get permanent tattoos develop strange skin growths. In 2008, University of Maryland researchers reported a case of a 38-year-old man who developed a skin tumor one month after getting a tattoo. In another study, published in 2010 in the Journal of Cutaneous Pathology, researchers analyzed eight people of tattoo-related skin tumors, and found that red tattoo ink was associated with most of the skin tumors. Experts say the skin recognizes the red ink as a foreign substance, and triggers an immune response.

Blisters, hives and swollen skin — from the sun

(Image credit: BSIP/UIG/Getty, File)

There are people who are allergic to the sun and experience symptoms such as blisters, hives and swelling of the skin when they’re exposed to it. According to a 2011 study from researchers in Germany, about 10 to 20 percent of people in Europe, United States and Scandinavia suffer from a sun allergy. The abnormal reaction to sunlight is usually due to ultraviolet rays, according to the Mayo Clinic.

Black spots on the skin

(Image credit: Poison Ivy photo via )

An itchy rash may be a common allergic reaction to poison ivy or poison oak, but there are also rare cases where people develop black spots, according to a 2008 study published in the journal Dermatitis. Black shiny deposits form on the skin and clothing when a high amount of resin, the toxic plants’ oily secretion, is exposed to the air. The researchers said the spots eventually peel off, and the skin heals without scarring.

Swollen tongue

(Image credit: Markson Sparks/Richard Neely/REX/, File)

People who have hay fever might have something besides hay itself to worry about: Some fruits and vegetables contain proteins similar to those found in hay pollen. They can cause allergies symptoms such as itchiness or swelling of the mouth, face, lip, tongue and throat. Known as oral allergy syndrome, the condition occurs when the immune system behaves as though the protein found in some fruits and vegetables and the pollen in the air are the same. The syndrome affects up to one-third of allergy sufferers and can occur at anytime, according to the American Academy of Allergy, Asthma and Immunology.

A bright red butt

(Image credit: Baboon photo via )

People exposed to certain metals, medications and plants or herbs, can develop Baboon Syndrome. That’s right, the condition means developing a bright red rash, primarily on the butt, closely resembling a baboon’s butt, according to research reports. The red rash can appear on the anus, genitals and inner thighs, and can be itchy and painful, but the syndrome doesn’t pose any serious health risks. Exposure to metals such as mercury, gold and nickel, can trigger a reaction, according to 2011 review in the American Journal of Clinical Dermatology. Recent studies have shown that antibiotics and antibacterials administered by mouth, intravenously or on the skin can also trigger the reaction.

Shortness of breath — thanks to onions?

(Image credit: Carsten Koall/Getty)

When you think of a physical reaction to onions, teary eyes probably come to mind.

But an onion farmer in Japan developed a cough and shortness of breath after spending too much time around the root veggies, according to a 2018 case report published in the journal Respiratory Medicine Case Reports.

It turned out that the man had allergy to a type of mold, called Aspergillus niger, that was growing on the onion peels. The mold can cause a condition called hypersensitivity pneumonitis, which occurs when the tiny air sacs in the lungs, known as alveoli, become inflamed.

The man’s symptoms went away when he wasn’t at work, and he was advised to wear a thick filtered mask while working with onions.

Originally published on Live Science.

Reaction signs and symptoms

Quick Facts

  • Do not ignore early symptoms.
  • Always take a possible reaction seriously and act quickly.
  • Not every reaction will always look the same; a person can have different symptoms each time.
  • Anaphylaxis can occur without skin symptoms or hives.
  • A child may describe their symptoms differently than an adult: for example “my throat is tingly” or “my tongue feels scratchy”.

An allergic reaction usually happens within minutes after being exposed to an allergen, but sometimes it can take place several hours after exposure.

Symptoms and severity of a reaction can differ each time. Keep in mind that an allergic reaction can start with mild symptoms that can get worse quickly.

Symptoms of anaphylaxis generally include two or more of the following body systems:

  • Skin: hives, swelling (face, lips, tongue), itching, warmth, redness
  • Respiratory (breathing): coughing, wheezing, shortness of breath, chest pain/tightness, throat tightness, hoarse voice, nasal congestion or hay fever-like symptoms (runny itchy nose and watery eyes, sneezing), trouble swallowing
  • Gastrointestinal (stomach): nausea, pain/cramps, vomiting, diarrhea
  • Cardiovascular (heart): paler than normal skin colour/blue colour, weak pulse, passing out, dizziness or lightheadedness, shock
  • Other: anxiety, sense of doom (the feeling that something bad is about to happen), headache, uterine cramps, metallic taste

However, a drop in blood pressure without other symptoms may also indicate anaphylaxis. It is important to know that anaphylaxis can occur without hives.

Make sure to talk to your doctor about how to recognize anaphylaxis.

The most dangerous symptoms of an allergic reaction are:

  • Trouble breathing caused by swelling of the airways (including a severe asthma attack for people who have asthma).
  • A drop in blood pressure causing dizziness, light-headedness, feeling faint or weak, or passing out.

Both can lead to death if untreated.


  • It is not possible to predict the severity of an allergic reaction.
  • Don’t ignore early symptoms, even if they seem mild, especially if you have had a reaction in the past.

Tips for parents

Small children can have a hard time describing their symptoms. They may complain of a “funny feeling” in their mouth or throat. Or, they may say things like “my mouth feels funny” or “my tongue is itchy”.

Emerging Allergen Reporting Tool

If your child has had a reaction in the last 12 months to a food other than a priority allergen, participate in an important research survey. Your participation will help researchers, and advocacy groups like ours, better understand emerging allergens.

Next, visit our Treating reactions page to learn how to treat allergic reactions.

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