What causes cold sores and how should they be treated?

Last Modified: 10/21/2021

We’re spending more time in the sun these days, and that can mean an increase in cold sores. The Parkview Pharmacy team helps explain why they occur and the best approach to treatment.

What are cold sores?

Cold sores are blisters that form on the skin around the lips and mouth. They are usually painful and occur due to an infection from the herpes simplex virus.

How are cold sores transmitted?

Cold sores are often caused by a different subtype of the herpes virus than the sexually transmitted infection. They are transmitted easily through contact with an infected individual by kissing or sharing items that touch the mouth such as silverware, drinks, towels, lip balm, etc.

What are the symptoms of a cold sore?

Cold sores are identified by the painful blisters that form near the lip/mouth area that eventually pop and scab over. The initial infection can be associated with systemic symptoms such as fever, body aches, sore throat or swelling in the neck. Recurrent episodes are more likely to have just the painful blisters without the other associated symptoms. People can often sense when a cold sore is about to form because they feel pain, tingling or burning around the lips 1-2 days before the blister appears.

How long do cold sores last?

During the initial episode, cold sores can last for 10-14 days. After the initial infection, the symptoms resolve and the virus becomes dormant. At certain times, for example, under periods of stress or direct exposure to sunlight, the virus can become reactivated and form more blisters. Recurrent infections are much shorter, lasting only about 5 days. Recurrent episodes often occur anywhere between 2 and 12 times per year.

How are cold sores treated?

Treatment for cold sores can fall into two categories: topical treatments or systemic treatments. Some topical treatments, such as docosanol (Abreva®), can be purchased without a prescription, while others, such as acyclovir (Zovirax, Sitavig) or penciclovir (Denavir) require a prescription. These treatments are usually creams that can be applied either directly to the cold sore, or if using Sitavig, a tablet placed under the lip, and can reduce the duration of the cold sore by about one day.

Systemic treatments consist of oral tablets or capsules that are taken for the duration of the cold sore and include agents such as acyclovir (Zovirax), valacyclovir (Valtrex), and famciclovir (Famvir). Like most other agents used to treat cold sores, all systemic treatments require a prescription for use. Systemic treatment has been shown to reduce the duration of cold sores by up to two days. Both topical and systemic treatments should be started as soon as possible and are most effective when used within 72 hours of developing a cold sore.

For those who have frequent recurrent infections (more than four times per year), systemic therapy can be used on a daily basis throughout the year to suppress viral reactivation. Generally, acyclovir or valacyclovir are used in these cases.

Should I see a doctor about my cold sores?

Generally, cold sores can be managed without going to the doctor as there are topical agents used to treat them that can be purchased without a prescription. However, you should see a doctor if:

  • You have severe symptoms or are unable to swallow liquids
  • Your cold sore does not resolve within a week (or 2 weeks if it is the initial episode)
  • You develop a cold sore and have one of the following conditions: HIV, cancer, organ transplantation, pregnancy, burn wounds, or other skin disorders. People with these conditions may have more severe and more frequent infections and are at an increased risk of the virus spreading to other areas of the body.
Remember …

The best way to avoid the discomfort of cold sores is to prevent them from occurring. If you have cold sores, do not kiss anyone or share food, drinks, towels, lip balm, etc with others, especially the high-risk individuals listed above. Remember to always consult label and package information prior to using any medication.

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