Cold Sores



Cold sores are caused by two types of herpes simplex viruses. Cold sores are common. Most people get the virus as young children.

The virus may be passed by:

  • Contact with the fluid from a cold sore or genital herpes sore of another person
  • Contact with the eating utensils, razors, towels, or other personal items of a person who has active cold sores
  • Sharing food or drink with a person who has active cold sores
  • Contact with the saliva of a person who has the herpes virus even if no sores are present

The first episode of illness with herpes virus can cause a body-wide illness. After that, the virus lies quietly in the skin until it is reactivated. The reactivated virus causes a cold sore to appear.

Risk Factors

Cold sores are more common in women, older adults, and people who are White.

Some things that can reactivate the virus and trigger an outbreak of cold sores are:

  • Infections
  • Fever
  • Physical injury or trauma
  • Menstruation
  • Pregnancy
  • A weakened immune system
  • Sun exposure
  • Physical or emotional stress
  • Dental or other oral surgery

It is not always known what triggers a cold sore.



Cold sores are most common on the lips, but they can also happen in the mouth or other areas of the skin. They are small and painful fluid-filled blisters.

A person may have itching, tingling, or burning the day before a cold sore appears. The sores will dry up with a crust and shallow sore after a few days.


The doctor will ask about symptoms and health history. The blisters will be examined.

A cold sore can usually be diagnosed by looking at it. Rarely, a sample of the blister may be taken for testing.

A blood sample may also be taken for testing.



There is no cure for the virus. The goal of treatment will be to manage symptoms and lower the risk of future outbreaks.

Cold sores will usually heal within 2 weeks even without treatment. Medicine may be given to ease symptoms, such as:

  • Over the counter cold sore creams and ointments
  • Mouthwash with lidocaine
  • Antiviral creams and ointments

Oral antiviral medicines may also be given to lower the risk of future outbreaks. Identifying and managing known triggers can also help.

People who have active cold sores should avoid touching them. This will lower the risk of the virus spreading to other parts of the body or to other people.


The risk of cold sores may be lowered by practicing proper handwashing after possible contact with the virus.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.