Cold sore

Cold sores — also called fever blisters — are common viral infections. They ‘re tiny, fluid-filled blisters on and around your lips. These blisters are usually grouped together in patches. When the blister splits, the crust forms over the resulting sore. Cold sores usually heal in two or four weeks without leaving a scar.

What are cold sores?

Cold sores are red, fluid-filled blisters that form near the mouth or on other areas of the face. In rare cases, cold sores may appear on the fingers, nose, or inside the mouth. They’re usually clumped together in patches. Cold sores may persist for two weeks or longer. A common virus called herpes simplex causes cold sores.

There’s no cure for HSV infection, and the blisters may return. Antiviral medications can help cold sores heal more quickly and may reduce how often they return.

Stages of a cold sore:

  • Stage 1: Tingling and itching occur about 24 hours before blisters erupt.
  • Stage 2: Fluid-filled blisters appear.
  • Stage 3: The blisters burst, ooze, and form painful sores.
  • Stage 4: The sores dry out and scab over causing itching and cracking.
  • Stage 5: The scab falls off and the cold sore heals.

Cold sore risk factors:

According to the Mayo Clinic, 90 percent of adults worldwide test positive for the herpes simplex type 1 virus. Once you have the virus, certain risk factors may reactivate it such as:

  • Infection, fever, or a cold
  • Sun exposure
  • Stress
  • HIV/AIDS or a weakened immune system.
  • Menstruation
  • Severe burns
  • Eczema
  • Chemotherapy.
  • Dental work.


Tingling and itching: Many people feel an itching, burning or tingling sensation around their lips for a day or so before a small, hard, painful spot appears and 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. Cold sores 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.

During first-time outbreaks, some people also experience:

  • Fever
  • Painful eroded gums.
  • Sore throat.
  • Headache
  • Muscle aches
  • Swollen lymph nodes


  • Viral infection or fever
  • Hormonal changes, such as those related to menstruation
  • Stress
  • Fatigue
  • Exposure to sunlight and wind
  • Changes in the immune system


Cold sores can also be treated with oral antiviral medications, such as acyclovir (Zovirax), valacyclovir (Valtrex), and famciclovir (Famvir). These drugs are available by prescription only.

Your doctor may instruct you to take antiviral medications regularly if you’re experiencing complications with cold sores or if your outbreaks are frequent.

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