Cold sore

Cold sores — also called fever blisters — are tiny, fluid-filled lesions that occur on and around your lips. These blisters are often grouped together in patches. After the blisters break, a crust forms over the resulting sore. Cold sores usually heal within two weeks.

Cold sores spread from person to person by close personal contact, such as kissing. Cold sores are caused by a herpes simplex virus (HSV-1) closely related to the one that causes genital herpes (HSV-2). Both of these herpes simplex viruses can affect your mouth or your genitals, and can be spread via oral sex.

There's no cure for HSV infection and the blisters may recur sporadically — often in response to stress or a weakened immune system. Antiviral medications can help cold sores heal more quickly and may reduce the frequency of recurrences.

Symptoms Causes Risk factors Complications Prevention

Most people who become infected with the virus that causes cold sores never develop symptoms. However, they still may be contagious to others, even without blisters.

For people who do develop signs and symptoms, a cold sore usually passes through several stages, which include:

  • Tingling and itching. Many people feel an itching, burning or tingling sensation around their lips for a day or two before cold sore blisters erupt.
  • Blisters. Small fluid-filled blisters typically break out along the border where the outside edge of the lips meets the skin of the face, although the blisters can also occur around the nose or on the cheeks.
  • Oozing and crusting. The small blisters may merge and then burst, leaving shallow open sores that will ooze fluid and then crust over.

Symptoms can vary, depending on whether this is your first outbreak or a recurrence. During first-time outbreaks, some people also experience:

  • Fever
  • Sore throat
  • Headache
  • Muscle aches
  • Swollen lymph nodes

Children under 5 years old may have cold sores inside their mouths and the lesions are commonly mistaken for canker sores. Young children are also more likely to spread the virus to other locations on their bodies, such as their fingers or around their eyes.

When to see a doctor

Cold sores generally clear up without treatment. However, see your doctor if:

  • You have a weakened immune system
  • The cold sores don't heal within two weeks
  • Symptoms are severe
  • You have frequent recurrences of cold sores
  • You experience irritation in your eyes

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