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 becomes dormant (an inactive state) in the nerve tissues in the face. Sometimes, the virus later reactivates, causing cold sores.

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

Herpes viruses spread most easily from individuals with an active outbreak or sore. You can catch this virus if you:

• Have intimate or personal contact with someone who is infected
• Touch an open herpes sore or something that has been in contact 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.

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

Symptoms may be mild or severe. They most often appear within 1 to 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 the 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 in the face or neck
• Painful swallowing

Blisters or a rash may form on your:

• Gums
• Lips
• Mouth
• Throat

When many blisters are present, it is called an outbreak. You may have:

• Red blisters that break open and leak
• Small blisters filled with clear yellowish fluid
• Several smaller blisters that may grow together into a large blister
• Yellow and crusty blister as it heals, which eventually turns 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 milder in most cases.

Your health care provider 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

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

Your 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, you may need 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 in a washcloth or a warm washcloth to the sores to help ease pain.
• Wash the blisters 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 fruit-flavored ice pops.
• Rinse with salt water.
• Take a pain reliever such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin).

Oral herpes most often 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 or medicines.

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

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

Contact your 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

Here are some tips to prevent mouth sores:

• Apply sunblock or lip balm containing zinc oxide to your lips before you go outside.
• Apply a moisturizing balm to prevent your lips from becoming too dry.
• 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. Both oral and genital herpes viruses can sometimes be spread, even when you do not have mouth sores or blisters.

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

Dinulos JGH. Warts, herpes simplex, and other viral infections. In: Dinulos JGH, ed. Habif's Clinical Dermatology: A Color Guide in Diagnosis and Therapy. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 12.

Schiffer JT, Corey L. Herpes simplex virus. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 135.

Whitley RJ, Gnann JW. Herpes simplex virus infections. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 345.

Updated by: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.