Cold sore; Fever blister; Oral herpes simplex; Herpes labialis; Herpes simplex
Oral herpes is an infection of the lips, mouth, or gums due to the herpes simplex virus. It causes small, painful blisters commonly called cold sores or fever blisters. Oral herpes is also called herpes labialis.
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:
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:
Before blisters appear, you may have:
Blisters or a rash may form on your:
When many blisters are present, it is called an outbreak. You may have:
Symptoms may be triggered by:
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:
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:
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.
The following steps can also help make you feel better:
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:
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:
Contact your provider if you have:
Here are some tips to prevent mouth sores:
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.
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.BACK TO TOP
Review Date: 7/8/2023
Reviewed 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.
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