Cause of fever blisters and how are they different from shingles?


What causes fever blisters on lips and how should they be treated? Also, what is the difference between fever blisters and shingles?

— Sores

Dear Sores,

Fever blisters, more commonly referred to as cold sores, can occur around a person's mouth, or on one's lips and face. These are commonly caused by the herpes simplex 1 virus (HSV-1). HSV-1 typically affects the mouth and facial areas, although it can be transmitted to the genital area, particularly through oral-genital sex. Shingles, on the other hand, is the colloquial term for herpes zoster and is caused by the varicella-zoster virus. Both conditions are a form of herpes, but they are caused by different forms of herpes virus and affect different areas of the body. Additionally, the ways in which they may become active in the body are also different. Ready for more? Keep on reading!

When it comes to HSV-1, it can be transmitted through direct contact with a lesion, through contact with fluid from a lesion, and through contact with the virus even when no symptoms are present in the infected person. Additionally, herpes simplex 2 (HSV-2) most commonly affects the genital area, but may also cause blisters on the mouth. The first herpes outbreak is usually the worst, may be accompanied by a fever, and tends to last the longest. After this outbreak, the virus lives in the nerve pathways around the area of the initial infection. The virus symptoms can and probably will recur at the same site; however subsequent outbreaks tend to be less serious than the first outbreak. Fever blisters may be reactivated because of circumstances such as direct trauma to the infected area, extensive sun exposure, elevated stress, fever, and hormone fluctuations.

While there are no cures for HSV-1 or HSV-2, cold sores typically resolve on their own in about two weeks. There are some medications (both prescription and over-the-counter) available to speed up the healing process. Some additional over-the-counter medications may alleviate pain, burning, and itching. Because active cold sores are very contagious, it's recommended that contact with others, such as kissing or sharing cups or utensils, (that come in contact with the cold sore) be limited. It’s also a good idea to make sure wash your hands frequently if you have to touch your cold sore, so that you don’t accidently transmit the virus to another part of your body, such as the eyes or genitals. Managing stress, eating well, being physically active, and getting adequate sleep are all ways to help prevent cold sores from recurring.

Herpes zoster, the medical term for shingles, is an infection of the nerves in areas of the skin by the varicella-zoster virus. Shingles differs from the herpes simplex viruses in that it's caused by a re-activation of varicella-zoster, the same virus responsible for causing chickenpox. After recovery from chickenpox, the varicella-zoster virus remains dormant (i.e., not active) in the body and, for undetermined reasons, may be reactivated later in life resulting in shingles. Characteristic symptoms of shingles include a painful rash of small, crusting blisters, most often on a strip of skin over the ribs on one side of the body (but can be found in other parts of the body as well).

Unlike herpes caused by HSV, shingles isn't transmitted from person to person. Interestingly, if someone who has never had chickenpox comes in contact with someone who has an active shingles case, they may develop chickenpox but not shingles. About one million Americans get shingles each year, making it a pretty common disease that mainly affects people over the age of 60 years. Shingles is also common in people with compromised immune systems; if you are older than 60 or your immune system is compromised, you may consider talking with your medical provider about getting the shingles vaccine, another way in which shingles differs from fever blisters.

If you're feeling discomfort from sores and you're not sure whether they're cold sores or shingles, speaking with a health care provider can be a great way to learn more. For more information about any of these types of blisters, check out the related Q&As and the Go Ask Alice! Herpes archives. Hope this helps!

Last updated Dec 16, 2022
Originally published Oct 20, 1995

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