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Skin Care and Diseases

Is it sun poisoning or fever blister?



I have noticed that this huge blister appears only in the spring/summer after sun exposure. I was recently diagnosed with fever blisters at the age of 33, never having them before. This "blister" occurs in the same spot, every time. It sometimes swells my entire top lip completely, where you think any minute it will pop. What do you think?


Your story fits best with herpes labialis - cold sores of the lips.  It is a known phenomenon that sunlight exposure causes mild immunosuppression and allows the expression of fever blisters.  You may be able to control the process by simply wearing a lip balm that contains sunscreens of at least SPF of 15, preferably though of 30.  If that is ineffective, you may wish to use zinc oxide which is an occlusive reflector which would probably prevent the activation of your herpetic lesions by sunlight. 

An additional option, may be the use of a prescription drug called Acyclovir.  Your board certified dermatologist, family medicine physician, or oral medicine physician could prescribe this for you.  I suggest that my patients use either Valacyclovir or Pentacyclovir.  When the first tingle begins, take the tablets.  These particular drugs are highly soluble and will often abort the development of the full blown blistering process.  In my office we like to culture the blisters to make certain that they are in fact herpes simplex. 


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Response by:

Charles L Heaton, MD
College of Medicine
University of Cincinnati