Causes

Oral herpes is a common infection of the mouth area. It is caused by the herpes simplex virus type 1 (HSV-1). Most people in the United States are infected with this virus by age 20.

After the first infection, the virus goes to sleep (becomes dormant) in the nerve tissues in the face. Sometimes, the virus later "wakes up" (reactivates), causing cold sores.

Herpes virus type 2 (HSV-2) usually causes genital herpes. However, sometimes HSV-2 is spread to the mouth during oral sex, causing oral herpes.

Herpes viruses spread easily. You can catch this virus if you have intimate or personal contact with someone who is infected. You can also catch it if you touch items infected with the herpes virus, such as infected razors, towels, dishes, and other shared items. Parents may spread the virus to their children during regular daily activities.

Symptoms

Some people get mouth ulcers when they first come into contact with HSV-1 virus. Others have no symptoms. Symptoms usually occur in kids between 1 and 5 years old.

Symptoms may be mild or severe.

They usually appear within 1-3 weeks after you come into contact with the virus. They may last up to 3 weeks.

Warning symptoms include:

• Itching of the lips or skin around mouth
• Burning near the lips or mouth area
• Tingling near the lips or mouth area

Before blisters appear, you may have:

• Sore throat
• Fever
• Swollen glands
• Painful swallowing

Blisters or a rash may form on your:

• Gums
• Lips
• Mouth
• Throat

Many blisters are called an "outbreak." You may have:

• Red blisters that break open and leak
• Small blisters filled with clear yellowish fluid
• Several smaller blisters may grow together into a large blister
• As the blister heals, it gets yellow and crusty, eventually turning into pink skin

Symptoms may be triggered by:

• Menstruation or hormone changes
• Being out in the sun
• Fever
• Stress

If the symptoms return later, they are usually more mild.

Exams and Tests

Your doctor or nurse can diagnose oral herpes by looking at your mouth area. Sometimes, a sample of the sore is taken and sent to a laboratory for closer examination. Tests may include:

• Viral culture
• Viral DNA test
• Tzanck test to check for HSV

Treatment

Symptoms may go away on their own without treatment in 1 to 2 weeks.

Your health care provider can prescribe medicines to fight the virus. This is called antiviral medicine. It can help reduce pain and make your symptoms go away sooner. Medicines used to treat mouth sores include:

• Acyclovir
• Famciclovir
• Valacyclovir

These medicines work best if you take them when you have warning signs of a mouth sore, before any blisters develop. If you get mouth sores frequently, your doctor may tell you to take these medicines all the time.

Antiviral skin creams may also be used. However, they are expensive and often only shorten the outbreak by a few hours to a day.

The following steps can also help make you feel better:

• Apply ice or a warm washcloth to the sores to help ease pain.
• Wash the blister gently with germ-fighting (antiseptic) soap and water. This helps prevent spreading the virus to other body areas.
• Avoid hot beverages, spicy and salty foods, and citrus.
• Gargle with cool water or eat popsicles.
• Rinse with salt water.
• Take a pain reliever such as acetaminophen (Tylenol).

Outlook (Prognosis)

Oral herpes usually goes away by itself in 1 to 2 weeks. However, it may come back.

Herpes infection may be severe and dangerous if:

• It occurs in or near the eye
• You have a weakened immune system due to certain diseases and medications

Possible Complications

Herpes infection of the eye is a leading cause of blindness in the United States. It causes scarring of the cornea.

Other complications of oral herpes may include:

• Return of mouth sores and blisters
• Spread of the virus to other skin areas
• Bacterial skin infection
• Widespread body infection, which may be life threatening in people who have a weakened immune system due to atopic dermatitis, cancer, or HIV infection

When to Contact a Medical Professional

Call for an appointment with your health care provider if you have :

• Symptoms that are severe or that don't go away after 2 weeks
• Sores or blisters near your eyes
• Herpes symptoms and a weakened immune system due to certain diseases or medicines

Prevention

Here are some tips to prevent mouth sores:

• Apply sunblock or lip balm containing zinc oxide to your lips before you go outside.
• A moisturizing balm to prevent the lips from becoming too dry may also help.
• Avoid direct contact with herpes sores.
• Wash items such as towels and linens in boiling hot water after each use.
• Do not share utensils, straws, glasses, or other items if someone has oral herpes.

Do not have oral sex if you have oral herpes, especially if you have blisters. You can spread the virus to the genitals, causing herpes simplex virus 2, or genital herpes. Both oral and genital herpes viruses can sometimes be spread even when you do not have mouth sores or blisters.

Alternative Names

Cold sore; Fever blister; Oral herpes simplex; Herpes labialis; Herpes simplex

References

Haile-Mariam T, Polis MA. Viral illnesses. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 128.

Habif TP. Warts, herpes simplex, and other viral infections. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2009: chap 12.

Updated: 4/4/2012

Reviewed by: David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine.