Prevent a cold sore

By the way, doctor: Does lysine prevent cold sores?

Updated: April 3, 2019Published: March, 2007

Q. For years, I have had recurrent cold sores and took antiviral drugs to treat the outbreaks. A friend suggested that I take daily lysine. What’s the evidence that it works?

A. Cold sores (sometimes called fever blisters) are painful fluid-filled lesions on or near the lips that are caused by the herpes simplex virus (HSV). There are two kinds of HSV: HSV-1, which causes most cold sores, and HSV-2, which is mostly responsible for genital herpes. HSV-1 infection is very common and easily transmitted by kissing or other contact with saliva. Once you’re infected, the virus lays dormant in the nerve cells that supply sensation to the skin. When the virus becomes active, it travels to the skin surface and multiplies, causing an outbreak.

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The Causes of Cold Sores and How to Prevent Them

How Can You Help Prevent a Cold Sore?

The virus that causes a cold sore is highly contagious. One way to protect yourself — and others — is to avoid sharing personal items, especially during an outbreak. Personal items include food, drinks, eating utensils, clothes, towels, and even makeup. (1)

Also, avoid skin-to-skin contact during an outbreak. This includes abstaining from sexual activity until blisters heal and scab over. (1)

Even though cold sores often develop on or around the lips, the virus can also spread to other parts of your body. This might happen if you touch a cold sore and then touch another area of your body. (5)

As you wait for a cold sore to heal, make a concerted effort not to touch your sore. Understandably, you have to touch the sore to apply cold sore creams or ointments. Rather than use your finger, use a cotton swab to dab on creams. If using your finger, wash your hands with soap and water immediately after applying the medication. (5)

If your child has a cold sore, encourage them not to suck his or her thumb. Thumb-sucking could spread the virus to their hand. (1)

An outbreak is always a possibility once you’re infected with the virus that causes a cold sore. You can reduce the frequency of an outbreak by avoiding known triggers. These vary from person to person, so you’ll need to be observant to identify your individual triggers.

For example, you may experience outbreaks after strong sun exposure. If so, you can possibly prevent an outbreak by wearing sunblock or staying indoors during the heat of the day. On the other hand, if you have more outbreaks when you’re tired, improving the quality of your sleep may reduce your number of cold sores. (6)

Unfortunately, you may experience numerous outbreaks. If you have repeated cold sore outbreaks, speak with your doctor to see if you’re a candidate for suppressive therapy, as recommended by Amesh A. Adalja, MD, a senior scholar at Johns Hopkins Center for Health Security based in Pittsburgh.

If so, your doctor will prescribe an antiviral that you can take daily, such as: (7)

  • Xerese or Zovirax (acyclovir)
  • Valtrex (valacyclovir)
  • Famvir (famciclovir)
  • Denavir (penciclovir)

Cold sores: Diagnosis and treatment

How do dermatologists diagnose cold sores?

A dermatologist can often diagnose a cold sore by looking at it.

Your dermatologist may also swab a cold sore. Fluid from the sore can be examined to find out if you have a herpes virus called the herpes simplex virus (HSV). This is the virus that causes cold sores.

How do dermatologists treat cold sores?

To treat cold sores, a dermatologist may prescribe:

Antiviral medication: Cold sores are caused by a virus, so antiviral medications are used to treat them. Your dermatologist may prescribe medication that you:

  • Apply directly to the sores, such as docosanol cream or acyclovir cream

  • Take by mouth, such as acyclovir, valacyclovir, or famciclovir

For someone who has a serious outbreak and cannot get relief from the above, a dermatologist may prescribe an antiviral medication that you receive through an IV, such as foscarnet or cidofovir. You’ll be closely watched if one of these medications is necessary.

If you get cold sores often and have a weak immune system, your dermatologist may prescribe a prescription cream called penciclovir. It can reduce the time that you have cold sores. To work, you need to apply it to the skin with the first symptoms of a cold sore, such as burning or tingling.

Treatment tip

When applying medicine to cold sores, dermatologists recommend gently dabbing the medicine on with a clean cotton-tipped swab.

Pain medication: If you have a lot of pain, your dermatologist may prescribe a medication that you apply to the sores, such as lidocaine.

Sunscreen: While the sores are healing, it’s important to protect them from the sun. A lip balm with an SPF of 30 or higher and broad-spectrum protection can help protect your lips. Worn year round, this lip balm may help prevent new cold sores.

Treating cold sores has benefits. Treatment can shorten your outbreak. It may even prevent you from getting a cold sore if you start treatment at the first sign of a cold sore (a tingling or burning sensation on your skin).

Treatment can also reduce your risk of spreading the virus to others.

Treatment is highly recommended if you get a cold sore and have:

  • Atopic dermatitis (usually begins in childhood and is often called eczema)

  • Sores near your eyes

  • A lot of cold sores

  • A lot of pain

  • Sores that spread to another part of your body, such as your hands or genitals

  • HIV, AIDS, cancer, or another disease that weakens your immune system

  • Cancer and are getting chemotherapy

  • To take medication that suppresses your immune system, such as medicine to control severe psoriasis or prevent organ rejection

  • Cold sores frequently

  • An outbreak that lasts more than two weeks

It’s important to treat cold sores if you have any of the above because the cold sores may not go away without treatment. Left untreated, the virus that causes cold sores can spread to other parts of your body. Some people develop another illness and become very sick.

If you’re healthy, you can treat cold sores on your own. Find out what dermatologists recommend at, Cold sores: Self-care.

What is the outcome for someone who has cold sores?

Cold sores cannot be cured. Some people get the virus and have just one outbreak. Others continue to get cold sores.

If you get cold sores several times a year, tell your dermatologist. A prescription antiviral medicine may help. Taking this medicine at the start of a cold-sore outbreak can shorten the amount of time you have cold sores. Some people who get cold sores frequently take this medicine every day. Taken daily, it can help prevent outbreaks of cold sores.

Fatahzadeh M and Schwartz RA. “Human herpes simplex virus infections: Epidemiology, pathogenesis, symptomatology, diagnosis, and management.” J Am Acad Dermatol. 2007;57(5):737-63.

Kissing and Cold Sores: What Are the Rules?

Cold sores are small blisters and sores that can develop on and around the lips. They’re known medically as “herpes labialis” and they’re an extremely common occurrence, with about 2.5 out of every 1,000 people experiencing at least one outbreak per year. Like other forms of herpes sores, cold sores are caused by the HSV-1 or HSV-2 viruses. Most cases of cold sores are the result of HSV-1, which affects more than two thirds of people aged 49 or below. Cold sores typically heal on their own, usually over the course of one to two weeks. Most people that develop cold sores will experience occasional relapses, as the virus that causes cold sores remains dormant in the body even when you don’t have any physical symptoms. Like all forms of the herpes simplex virus, cold sores are highly contagious. Kissing and cold sores is risky business, because if you kiss someone while you have one or more cold sores, there’s a significant risk the other person being exposed to and infected by the virus.

In this guide, we’ll explain how cold sores can transmit HSV-1 (and less frequently, HSV-2) from one person to another. We’ll also explain when it’s safe to kiss someone, engage in oral sex, or have any other kind of oral contact after a cold sore.

How Do Cold Sores Spread?

Cold sores spread through contact with infected people. Since cold sores are so prevalent, most people are already infected with the HSV-1 virus that causes them. In fact, most data shows that around two thirds of all people aged 14 to 49 are infected with the HSV-1 virus.

Most people are infected with HSV-1 without ever realizing, often through contact with a sexual partner or an innocent kiss from a relative that unintentionally transmits the virus.

Even if you already have HSV-1 (or, less frequently, HSV-2), you might not ever develop a cold sore. This is because only a small percentage of people infected with HSV-1 or HSV-2 develop physical symptoms, such as oral herpes (cold sores) or genital herpes.

Still, it’s important to take precautions to prevent cold sores from spreading, even if you’re fairly confident you or your partner already have HSV-1. Often, kissing someone with a cold sore can trigger an outbreak in another individual even if they’re already infected with the herpes virus.

The Eight Stages of a Cold Sore

Cold sores usually take one to two weeks to heal. During this healing period, they’ll go through a consistent process, starting as a small blister on the lip that develops into an open sore before it heals over. So, even then, if your question is, “Can you kiss someone with a cold sore scab?” the answer is a definitive hard no.

In fact, the development and healing process for a cold sore can be divided into eight stages, all of which have the potential for the virus to shed and spread to other people:

  • The first stage is the latent period. In this stage, the herpes virus is dormant in the body and you, if you’re infected with the virus, won’t notice any symptoms. During this stage, your body may still be shedding the HSV-1 or HSV-2 virus even without symptoms.
  • The second stage is the prodromal stage. During this period, people often experience a tingling sensation on or around the lips and red skin in the affected area. This stage lasts for one to two days in most people. It’s in this phase that you’re most likely to stop a herpes outbreak in its tracks. But even then, you’re still contagious.
  • The third stage is the inflammation stage. At this point, if you haven’t taken proper precautions in the prodromal stage, the herpes virus targets cells in the lips or mouth, beginning the process of creating a sore. This takes around one day, with swelling and discomfort in the affected area.
  • The fourth stage is the pre-sore stage. Over the course of one to two days, a small, hard blister will begin to develop on or around the lips. These blister are often painful and can make eating, chewing and moving the lips uncomfortable for the affected person.
  • The fifth stage is the open herpes lesion stage. During this period, the blister (or blisters, if you have multiple sores) will open into an exposed sore. Most cold sores remain open for one to two days, during which they are highly infectious.
  • The sixth stage is the crusting stage. At this point, the body’s immune system begins to actively heal the sore by developing a brown, immunoglobulin crust. It usually takes two to three days for the crust to develop into a scab.
  • The seventh stage is the healing stage. At this point, a scab has fully enveloped the sore and new skin is developing underneath. The scab will typically remain for up to five days, during which the cold sore is still infectious.
  • The eighth and final stage is the post-scab stage. At this point, the sore will have healed and the skin will be returning to normal. It’s still possible for some redness to linger in the affected area for two to three days.

While cold sores usually develop on or around the lips, they can also develop inside the mouth—a form of herpes infection called herpetic stomatitis.

Cold sores are contagious at all stages of the development and healing process, meaning you shouldn’t kiss anyone, share eating utensils, have oral sex or engage in any other oral contact throughout the entire process of a cold sore developing and healing. Kissing and cold sores (and any other physical activity during or after the outbreak) is dangerous business.

When is it Safe to Kiss Someone After a Cold Sore?

When is a cold sore healed enough to kiss? The short answer is that it’s not. In general, it’s best to wait for three to four days after the cold sore scab disappears before you kiss someone or engage in oral sex. This is because the herpes virus can continue shedding in the late stages of a cold sore healing, even if there’s no viral fluid present.

The longer you wait after an outbreak, the lower your risk of transmitting cold sores to a partner or other person. As always, it’s best to be patient and wait for the outbreak to completely clear up before you put yourself in a situation where spreading the virus is possible.

Speeding Up The Cold Sore Healing Process

Cold sores can be extremely annoying, especially if they get in the way of you being intimate with your partner. Unfortunately, they can also carry a social stigma, making meetings, lunch with friends and other normal situations embarrassing and stressful.

There are several highly effective medications on the market that you can use to speed up the healing process and treat cold sores when they flare up. Often, treating a cold sore in its early stages (the prodromal stage) can prevent it from fully developing.

Of these medications, the most widely used is valacyclovir. Our Valacyclovir 101 guide covers everything you need to know about using valacyclovir to treat cold sores, from the medication’s mechanism of action in the body to common dosage periods, side effects and more.

Treatment options for cold sores in the early stages

Share on PinterestTreating a cold sore as soon as it appears is recommended to minimize the outbreak.

Though cold sores cannot be avoided all the time, people should always try to treat them as soon as they can.

Treating a cold sore in its earliest stage can result in a smaller sore that heals quickly.

Ideally, the cold sore may be stopped in its tracks, so it never appears at all.

The following steps can help stop a cold sore early or minimize the outbreak.

Know the early signs of a cold sore

Most people who get cold sores report that they can feel one coming before it appears on their skin. So, people who have them should watch for signs that a cold sore may be developing.

Tingling, burning, or itching may be felt around the lips for several hours or a day before the cold sore appears. This is the best time to begin treating the cold sore.

Keep antiviral medications on hand

People who frequently get cold sores may want to have the appropriate medications on hand so that they can begin using them at the earliest possible stage.

The medicines that have been proven to work on cold sores are called antivirals, and they work to stop a virus from replicating. This, in turn, can stop the cold sore from developing or may reduce its size and healing time.

Antiviral medications are only available with a prescription. Cold sore antivirals come in two different forms:

  • topical medication (cream) that is applied directly to the area
  • oral medications (pills) that are taken by mouth

Antivirals are well-tolerated by most people. However, not everyone can or should take antivirals. The benefits and risks must be discussed with a doctor.

People may wish to have a prescription filled out and ready rather than wait for the next cold sore to appear before they ask for one. This way, the medication can be taken or applied as soon as the tingling or other symptoms begin.

Antivirals work best when used as early as possible before the cold sore can even be seen.

Get to know cold sore triggers

Due to their potentially embarrassing nature, many people look to get rid of cold sores overnight.

However, preventing a cold sore is quicker and safer approach than treating an outbreak. People can try to avoid triggers that cause cold sores, keeping the sores on their skin from appearing in the first place.

Preventing a cold sore may also help reduce the risk of spreading the virus to other people.

Not all cold sores can be prevented, but knowing what triggers them is an important step in cold sore management. Common cold sore triggers include:

  • certain foods
  • stress
  • an illness or surgery
  • lack of sleep
  • sun exposure or wind
  • injury to the skin
  • hormonal changes, especially from menstruation or taking birth control pills
  • a weakened immune system

Keeping a diary or log may help a person work out what triggers their cold sores. Writing down things, such as diet, activities, illnesses, and life events can help narrow down what has preceded the outbreak.

An added benefit of knowing cold sore triggers is the ability to be even more proactive in taking medications. Consequently, if a person knows they were exposed to a cold sore trigger, they can be especially watchful for early signs and get started on medications right away, if needed.

Consider home remedies and over-the-counter products

Antiviral medications may only be prescribed for those who have recurrent cold sores. For an occasional sore that does not need a prescription medication, over-the-counter products or natural remedies may help with healing and appearance.

Some steps that people can take to treat cold sores early include the following:

  • Docosanol (Abreva) is an over-the-counter treatment that may shorten a cold sore’s duration. Like prescription medicines, it works best when taken at the earliest stage. Abreva can also be purchased online.
  • Other over-the-counter cold sore products that contain tea tree oil, menthol, and antibacterial agents may also be helpful in managing the pain. Various products are available to purchase online.
  • Rubbing alcohol and hydrogen peroxide may help dry out the sore and speed up healing. People should stop using it, however, if it causes more pain or irritation.
  • Topical or oral numbing medicines, which can be purchased in stores, can help with discomfort. These may be safe for children, but caregivers should ask a pediatric doctor before using them on a child.
  • Cold packs, ice, or cold foods and drinks may help soothe the area. They may also help with the healing process by fighting inflammation.

Measures for preventing cold sores

This review included 32 RCTs, with a total of 2640 immunocompetent participants, covering 19 treatments. The quality of the body of evidence was low to moderate for most outcomes, but was very low for a few outcomes. Our primary outcomes were ‘Incidence of HSL’ and ‘Adverse effects during use of the preventative intervention’.

The evidence for short-term (≤ 1 month) use of oral aciclovir in preventing recurrent HSL was inconsistent across the doses used in the studies: 2 RCTs showed low quality evidence for a reduced recurrence of HSL with aciclovir 400 mg twice daily (risk ratio (RR) 0.26, 95% confidence interval (CI) 0.13 to 0.51; n = 177), while 1 RCT testing aciclovir 800 mg twice daily and 2 RCTs testing 200 mg 5 times daily found no similar preventive effects (RR 1.08, 95% CI 0.62 to 1.87; n = 237; moderate quality evidence and RR 0.46, 95% CI 0.20 to 1.07; n = 66; low quality evidence, respectively). The direction of intervention effect was unrelated to the risk of bias. The evidence from 1 RCT for the effect of short-term use of valaciclovir in reducing recurrence of HSL by clinical evaluation was uncertain (RR 0.55, 95% CI 0.23 to 1.28; n = 125; moderate quality evidence), as was the evidence from 1 RCT testing short-term use of famciclovir.

Long-term (> 1 month) use of oral antiviral agents reduced the recurrence of HSL. There was low quality evidence from 1 RCT that long-term use of oral aciclovir reduced clinical recurrences (1.80 versus 0.85 episodes per participant per a 4-month period, P = 0.009) and virological recurrence (1.40 versus 0.40 episodes per participant per a 4-month period, P = 0.003). One RCT found long-term use of valaciclovir effective in reducing the incidence of HSL (with a decrease of 0.09 episodes per participant per month; n = 95). One RCT found that a long-term suppressive regimen of valaciclovir had a lower incidence of HSL than an episodic regimen of valciclovir (difference in means (MD) -0.10 episodes per participant per month, 95% CI -0.16 to -0.05; n = 120).

These trials found no increase in adverse events associated with the use of oral antiviral agents (moderate quality evidence).

There was no evidence to show that short-term use of topical antiviral agents prevented recurrent HSL. There was moderate quality evidence from 2 RCTs that topical aciclovir 5% cream probably has little effect on preventing recurrence of HSL (pooled RR 0.91, 95% CI 0.48 to 1.72; n = 271). There was moderate quality evidence from a single RCT that topical foscarnet 3% cream has little effect in preventing HSL (RR 1.08, 95% CI 0.82 to 1.40; n = 295).

The efficacy of long-term use of topical aciclovir cream was uncertain. One RCT found significantly fewer research-diagnosed recurrences of HSL when on aciclovir cream treatment than on placebo (P < 0.05), but found no significant differences in the mean number of participant-reported recurrences between the 2 groups (P ≥ 0.05). One RCT found no preventive effect of topical application of 1,5-pentanediol gel for 26 weeks (P > 0.05). Another RCT found that the group who used 2-hydroxypropyl-β-cyclo dextrin 20% gel for 6 months had significantly more recurrences than the placebo group (P = 0.003).

These studies found no increase in adverse events related to the use of topical antiviral agents.

Two RCTs found that the application of sunscreen significantly prevented recurrent HSL induced by experimental ultraviolet light (pooled RR 0.07, 95% CI 0.01 to 0.33; n = 111), but another RCT found that sunscreen did not prevent HSL induced by sunlight (RR 1.13, 95% CI 0.25 to 5.06; n = 51). These RCTs did not report adverse events.

There were very few data suggesting that thymopentin, low-level laser therapy, and hypnotherapy are effective in preventing recurrent HSL, with one to two RCTs for each intervention. We failed to find any evidence of efficacy for lysine, LongoVital® supplementation, gamma globulin, herpes simplex virus (HSV) type I subunit vaccine, and yellow fever vaccine in preventing HSL. There were no consistent data supporting the efficacy of levamisole and interferon, which were also associated with an increased risk of adverse effects such as fever.


Cold sores are caused by a common virus called herpes simplex. Most people get exposed to the virus when they’re babies or children. There’s no cure for it. Once you’ve been exposed to it, it’s always in your system, even if it doesn’t often cause cold sores or other symptoms.

Herpes simplex is spread by close contact. If you kiss someone with a cold sore, or you touch his face and then touch your own face, you can catch the virus. You can also get herpes simplex by sharing lip balm, a fork, a mug or a razor with someone who has it. You’re most likely to get the virus from someone who has an active cold sore, but it’s also possible to contract it from someone who doesn’t have a sore or blister showing.

The virus also can spread to the eyes or the genitals. For example, if you rub your eyes after getting saliva from an infected person on your hands, or if you receive oral sex from someone who has cold sores.

When you’re first exposed to the virus, you’re likely to get a cold sore. After a week or two, it’ll go away on its own. Then the virus goes dormant in your body. You may never have another cold sore outbreak again, but many people do.

Some things that make an outbreak more likely are:

  • A cold or other illness
  • A fever
  • Stress
  • Too much sun
  • Your period

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