A cold sore is a single or group of small blisters that appears on the lip or around the mouth and is caused by reactivation of the herpes simplex virus (HSV). More than half of Americans carry the HSV virus, and a cold sore happens when the virus reactivates from lying dormant in sensory nerves. Most people catch the virus when they are a child, and some people never have a skin reaction at the time of infection. Symptoms of reactivation causing a cold sore often include a burning sensation, itching, or slight numbness. A cold sore usually clears on its own within about 2 weeks, but there are treatment options to help it clear faster or even to help prevent cold sores. Cold sores are contagious but are no longer contagious once scabbed over.
Sometimes there are triggers that can cause the cold sore virus to reactivate to cause a cold sore. These can include:
- Recent illness, such as a cold or the flu
- Dental work
- Destructive treatment by a dermatologist around the mouth
- Injury or cuts in the area prone to cold sores
- Cosmetic surgery or laser treatment
- Sunlight and sunburns
- Certain food
- Hormonal changes or menstrual cycles
Cold sores are usually diagnosed by a dermatologist just by looking, but sometimes a swab of an unbroken blister can be tested in the lab to confirm the diagnosis. Occasionally, a skin biopsy may be required to make the diagnosis if the appearance or location is atypical.
Cold sores are treated with antiviral medication. Medications that can be applied topically are available over the counter and work better for some people than others. Oral antiviral medication will be prescribed by your dermatologist, and may include acyclovir, valacyclovir, or famciclovir. These may be provided to be taken in high dose at the onset of a new breakout or at a lower dose every day to help prevent breakouts. Sunscreen is very important to help prevent breakouts. The pain of a cold sore can be lessened by applying ice chips, a non-prescription gel or ointment containing benzocaine, lidocaine, dibucaine, or benzyl alcohol, or taking ibuprofen or acetaminophen. Avoiding acidic or spicy foods during an outbreak is recommended. Ointment such as Aquaphor or Vaseline will help heal cracked or crusted skin and can help reduce associated pain.