Q. I seem to react badly to flea bites or bites from other insects. The bites on my lower legs and ankles become red and swollen and last for days to weeks. When the bites finally clear, they leave a round dark spot that can last for months.

What causes this reaction, and is there anything I can do about these spots?

A. Your reaction is what doctors call post-inflammatory hyperpigmentation. This is a fancy way of saying that you have a tendency to develop dark spots on your skin in areas that have become reddened, inflamed or damaged in some way.

Oddly enough, some people may also react by developing light spots instead of dark spots, in which case they have post-inflammatory hypopigmentation ("post" means after, "hypo" means decreased and pigmentation refers to the natural coloring substances in your skin).

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Both the light and dark spots will tend to fade in time and become more like the surrounding skin. But they may also last indefinitely. If so, there are a couple of things you can do for the dark spots if they bother you enough. (I don't know of anything that works well for light spots.)

One is to use a skin-lightening agent like hydroquinone. This chemical is contained in over-the-counter skin products like Eldopaque, Esoterica or Solaquin; it's also the active ingredient in prescription skin lighteners like Eldopaque Forte or Solaquin Forte. For best results, you should also use a sun-block lotion on any sun-exposed areas that have dark spots to keep them from growing darker. Some skin-lightening creams already come with sunscreen in them.

Besides hydroquinone, some doctors have also prescribed the anti-acne cream Retin-A for African Americans to treat dark spots that follow inflammation in the skin.

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Whether you have light or dark spots after a bite, acne or other types of skin inflammation, it may be worth waiting a while to see how much your skin coloring gradually evens out.

Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington.

Consultation is a health education column and is not a substitute for medical advice from your physician.

Send questions to Consultation, Health Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Questions cannot be answered personally.

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