Cold sores


An unwelcome visitor

You can feel it begin. A stinging, tingling, even itching sensation near your mouth. Soon a cold sore appears. Cold sores are caused by a dormant herpes virus "awakened" by a weakness in the immune system. These sores can be painful and unsightly, and are highly contagious. Unlike canker sores that form on the inside of the mouth, cold sores usually form on the lips and around the mouth, but can also appear near or in the eye or on the genitals.

Luckily, the symptoms can be treated and the sores will heal on their own over time.

Detailed Description

Herpes sores are small, contagious, painful blisters that occur on and around the mouth, the cornea, and sometimes the finger or genitals. Most blisters appear with a red ring around them. During their course, the blisters fill with fluid, crust over, dry up, and eventually disappear. If you are dealing with an outbreak in or near the eye, it is important to consult your doctor immediately to avoid permanent damage. Avoid contact or rubbing of the eye. Also, genital breakouts should be examined and treated by a physician. Read more about genital herpes.

Cold sores are usually caused by one of two types of herpes. Type 1 herpes simplex virus is the most common cause, though Type 2 has also been known to be accountable. Type 2 is the same virus that is responsible for outbreaks of genital herpes. Most people have a strain of the herpes virus in their system for years without having an outbreak of cold sores. The virus lies dormant in the body because of antibodies that control it. Cold sores occur when there is a strain on or breakdown in the immune system, which can be caused by the following:

  • Sunburn
  • Stress
  • A cold
  • Intestinal infection
  • Menstruation
  • An immune deficiency like AIDS

Characteristics of Cold Sores

Cold sores are small, contagious, painful blisters on and around the mouth, cornea, or genitals that start out as red, irritating eruptions, then fill with fluid, crust over, dry up, and eventually disappear. Most sores heal naturally in about two week's time. More persistent sores may be signs of a secondary infection, and should be treated as such. Consult your doctor if you are unsure of your condition. Also, those with eczema are more likely to experience severe outbreaks.

How Common Are Cold Sores?

An examination of blood serum tests indicates that approximately 85% of adults have antibodies to (meaning they have been exposed to) herpes simplex virus 1 (HSV-1), while 25% to 65% have herpes simplex virus 2 (HSV-2). All age groups may be infected, and incidence is equal in both males and females.

What You Can Expect

Most outbreaks of cold sores will heal on their own over time. However, steps can be taken to help relieve the associated pain. Cold sores are also highly contagious, so it's important to prevent spreading the virus. Washing your hands frequently and separating your utensils and linens can help.

If you are experiencing an infection in or around the eye, it is important to get immediate treatment. Your doctor may prescribe antiviral eye drops or ointments containing such antiviral agents as vidarabine (Vira-A), trifluridine (Viroptic), or idoxuridine (Herplex Liquifilm and Stoxil). Medication should be applied several times a day to help prevent eye damage.

Conventional Treatment

Goals of Treatment

The herpes virus cannot be cured. It remains in your system even after sores have healed and disappeared. Research is being done to develop a vaccine. However, by using antiviral agents and containing the virus, cold sores can be treated effectively to control the pain associated with them, limit further exposure and risk of spreading the virus, and to avoid a secondary infection.

Treatment Overview

Treatment lasts for five to 10 days on an outpatient basis. Because of the contagious nature of this virus, it is extremely important to limit exposure when experiencing an attack. This means keeping the affected areas clean, as well as keeping utensils and linens separate from those used by others. Be extremely cautious around small children and infants, or those taking immunosuppressant medications. You are infectious until a blister crusts or scabs over.

Current Drug Therapies Available

The pain of a cold sore can be treated easily with acetaminophen (Tylenol) or another over-the-counter pain killer.

Your doctor may also prescribe an antiviral agent like acyclovir (Zovirax) to help treat the sores themselves. Zovirax capsules can make an outbreak heal slightly faster. In case of recurrent chronic herpes, it can be taken every day for up to 12 months or longer to reduce the severity and frequency of future attacks. Over-the-counter petroleum salves can be applied to help keep scabs soft while a sore heals. Oral acyclovir is not generally given for minor fever blisters.

If you are experiencing an infection in or around the eye, it is important to get immediate treatment. Your doctor may prescribe antiviral eye drops or ointments containing such antiviral agents as vidarabine (Vira-A), trifluridine (Viroptic), or idoxuridine (Herplex Liquifilm and Stoxil). Medication should be applied several times a day to help prevent eye damage.

Drug Therapy

Drugs most commonly prescribed

Antiviral drugs are effective agents for treating cold sores. (These virtually nontoxic drugs are even more effective in treating genital herpes.) They include the following:


On-Label Efficacy


On-Label Efficacy


On-Label Efficacy

Treatment usually lasts between five and 10 days. Continue taking the medication until you have finished the prescribed amount, even if your symptoms begin to disappear.

If you experience severe recurrences of symptoms, long-term suppressive antiviral drug therapy is the most effective means of controlling outbreaks. Suppressive treatment will reduce the number of outbreaks by about 85%. A significant number of patients are able to discontinue medication after a period of five or seven years.

Second choices

Oral anesthetics, such as benzocaine and lidocaine, can be applied directly to numb the sores, enabling you to eat and drink more comfortably. Ibuprofen and aspirin can also help relieve minor pain and subdue inflammation. However, pregnant women and people with ulcers should avoid using these drugs, unless explicitly instructed to do so by their doctors.

Drugs commonly prescribed to treat particularly delicate and sensitive regions are vidarabine, which is effective in treating herpes simplex viral infection of the eye, and penciclovir, a cream used to treat oral herpes infections.


On-Label Efficacy

Healthcare Professionals Who May Be Involved in Treatment

  • General practitioners
  • Dermatologists

Activity and Diet Restrictions

The main restriction with cold sores is to prevent spreading by physical contact — especially kissing. It is also important to be careful during sexual contact. The herpes virus can be transmitted through oral-genital contact, so this form of sexual contact should be avoided, or a latex barrier (like a dental dam or condom) should be used to help prevent transmission.

It helps to avoid salty and acidic foods until the blisters have completely healed. Cool liquids, frozen juice bars, and yogurt have all been found to help soothe cold sores.

Monitoring the Condition

Except in severe cases of viral infection warranting extensive medical attention, self-monitoring is generally appropriate. In general, look for the gradual disappearance of lesions and monitor the efficacy of any medications you are taking.

Possible Complications

Cold sores themselves do not cause these complications, but the virus that cause the cold sores does. Most commonly, a secondary bacterial infection can develop. If the virus infects the eyes, a condition known as keratitis, or inflammation of the cornea, can develop. Keratitis can lead to blindness if not properly treated. Inflammation of the fluid-filled regions that envelop the brain and spinal cord (meningitis or encephalitis) can result if the virus infects the central nervous system.

Quality of Life

While cold sores may be irritating, painful, and unattractive, they shouldn't seriously affect your quality of life. They usually heal quickly and shouldn't leave any permanent scarring.

If you have sores on your genitals, open and honest communication with any sexual partners is essential. It is best to entirely refrain from any sexual contact during an outbreak. If you do engage in sexual activity when sores are present, use a latex barrier (such as a condom) to help prevent the virus from spreading to your partner.

Considerations for Women

Women seem to have a higher risk of outbreak during and near the time of their menstrual periods.

Considerations for Children and Adolescents

It is important for children to avoid close contact with those who have cold sores.

Also, do not give aspirin to anyone under age 18 during a viral infection, due to an increased risk of Reye's syndrome, a serious and potentially life-threatening disorder.

Considerations for Older People

With age, the immune system becomes weaker and often allows more probability of infection. Older individuals are more sensitive to medications, so let your doctor and pharmacist know which medications you are already taking before using anything prescribed for cold sores.

Cold sores

Last updated 27 May 2012


  • Fever blisters
  • Herpes simplex


Established Causes

HSV-1 more commonly causes oral lesions, although both types 1 and 2 can cause cold sores. Likewise, both types can cause genital lesions, although type 2 is most often responsible for those.

Drugs That Can Cause or Aggravate Cold Sores

Any class of drug that suppresses the immune system (immunosuppressants) can precipitate an outbreak of a dormant herpes virus.

Risk Factors

Existing skin conditions, overexposure, or any factor that depresses your body's immune system can increase your risk of breaking out in a cold sore. Following is a complete list of risk factors:

  • AIDS
  • Eczema in children
  • Increased stress levels
  • Illness, including:
    • Common cold
    • Minor gastrointestinal upset
    • Fever (hence the name fever blister)
  • Excessive sun exposure
  • Menstruation
  • Aggressive oral manipulation; for example, dental treatment that stretches a person's mouth
  • Use of immunosuppressive drugs

Symptoms & Diagnosis

Signs that can alert you to impending viral activity 24 to 36 hours prior to an actual outbreak include tingling sensations and increased sensitivity around the area soon to be infected. During an outbreak, the infected area begins to burn and blister, as characterized by the formation of reddish, pus-filled sores that frequently merge into a large ulceration. The swollen area later breaks open, scabs over, and sloughs off within a few days, leaving no signs of residual damage.

Oral sores appear most frequently in the area immediately surrounding the lips, but the infection can spread to the nostrils, inside the mouth, and to areas around the eyes. Genital herpes sores typically form on the penis, the labia, the skin immediately surrounding the anus, and the buttocks. Herpes simplex is the principal cause of genital ulcerations in people with AIDS.

Conditions That May Be Mistaken for Cold Sores

Any number of infectious skin conditions that produce lesions may preclude a diagnosis of herpes simplex virus. These include the following:

  • Impetigo: A skin infection characterized by a red rash and spotted by many small straw-colored blister
  • Canker sore: Shallow ulcerations infecting the fleshy parts inside the mouth
  • Herpes zoster (or chickenpox): A different type of herpes virus that produces tiny, blister-like lesions on the body and, occasionally, the face
  • Aphthous stomatitis: A disorder targeting the anterior portions of the mouth, characterized by shallow grayish erosions surrounded by a ring of red
  • Syphilis-related lesions
  • Herpangina: A common disease among children, characterized by fever and vesicular and ulcerative lesions in the throat that may progress to areas of the mouth and lips
  • Kaposi's varicelliform: A disease resembling chicken pox that affects the skin and mucous membranes

How Cold Sores Are Diagnosed

Cold sores are often successfully diagnosed through a self-examination and observance of symptoms. If you suspect that your symptoms do not conform to those typically associated with herpes simplex virus, a biopsy and laboratory evaluation can resolve any doubts.

Laboratory Work

Clinically available antibody tests fail to distinguish between herpes simplex virus types 1 and 2, but help rule out suspicion of a primary infection. Viral cultures and immunofluorescent antibody slide tests offer a rapid and sensitive diagnosis and can differentiate between type 1 and type 2. A Tzanck smear is also useful in confirming the presence of a herpes virus, although it fails to distinguish between various types.

Alternative care


One amino acid, arginine, increases replication of the herpes virus that causes cold sores, while another amino acid, lysine, helps prevent this. Several studies show that avoiding foods high in arginine and taking supplemental lysine (see below) may be helpful. Foods high in arginine include grains, cereals, nuts, seeds, chocolate, beer, and soft drinks.


Lysine: Studies showing the benefit of a low-arginine/high-lysine approach typically include lysine supplementation of 500 to 1,000 mg three times a day. NOTE: Lysine supplements may raise cholesterol levels. If yours is elevated, do not try this treatment. Consult your doctor first.


  • Garlic
  • Echinacea


Stress-management techniques, including meditation, biofeedback, visualization, and hypnotherapy, may help reduce the severity of cold sore outbreaks and prevent recurrences.

Self care & Prevention

Preventing Cold Sores

Since cold sores are caused by a contagious virus, you can prevent them by avoiding close physical contact with someone who is infected and has active lesions.

Kissing and oral-genital contact can spread the virus. You're also contagious from the moment you feel a sore beginning to erupt. Using a condom or other latex barrier during oral-genital contact may help to prevent the spread of the virus.

Avoid physical and emotional stress — you are most likely to have an outbreak when your immune system is weakened. Since sun exposure can trigger an outbreak, sunscreens of at least SPF 15 around the mouth area may help ward off flare-ups. And wear a broad-brimmed hat.

Self-Care Measures

If you already have a cold sore, you can relieve the pain in the following ways:

  • Steer clear of salty or acidic foods — they can aggravate the pain of cold sores.
  • An ice pack can help relieve the pain.
  • Aspirin, ibuprofen, and acetaminophen can also be used to treat cold-sore pain.