I have a spotty skin rash that is centered mainly around my chest. I went to a doctor who said it was a viral infection, and gave me antibiotics for it. It made no difference, and it is spreading very slowly. It does not itch and when it is exposed to the sun, the affected area does not tan.
As always when I am discussing rashes which people describe to me over email, I feel some discomfort since I cannot see the rash myself or ask any clarifying questions about it. With that caveat, let me say that the rash you are describing sounds most like a common fungus infection called Tinea versicolor.
Tinea is a generic term used to denote fungal infections of the skin. Tinea pedis is athlete’s foot, tinea capitis is ringworm on the scalp, etc. Versicolor in the name Tinea versicolor does not indicate the location of the rash, but rather its characteristic mottling, which I believe is what you are referring to as spotty.
T. versicolor is very common in adolescents and young adults. The fungus causing it is Pityrosporum orbiculare, which is a normal inhabitant of the skin and scalp. Why some people get the rash and others don’t is a mystery, since we probably all carry the fungus. It is also not known why the occurrence of the rash seems to be less as we age. The rash is commonly found on the shoulders, neck, chest, abdomen and occasionally on the face. Many people are not aware of having it because it may be hardly noticeable until one is exposed to sun. Skin affected by T. versicolor does not tan, as you mentioned, so the blotchy areas affected by the fungus stand out from the tanned skin around them.
The rash is usually aysmptomatic, although occasionally it may itch slightly when one is hot and sweaty. It is not dangerous, does not invade the body internally, and does not tend to become superinfected by more dangerous organisms. However the blotchy character of it can be unsightly, particularly at the beach. It is not contagious in the usual sense of the term, meaning that you catch it from someone else, since most of us carry the fungus to begin with, and other factors determine if we get the rash.
There are a number of treatments available to get rid of T. versicolor, at least temporarily. Any of the antifungal creams or liquids are effective. I prefer the liquids since it may be necessary to cover a fair amount of affected skin. Some brand names that are available over the counter include Lamisil AT solution, Lotrimin solution or Tinactin. Two weeks of twice daily applications may be required. Selenium sulfide 2.5 percent shampoo usually used for dandruff is also effective. It is applied full strength at night and washed off in the morning, and usually works in three to four days. It unfortunately requires a prescription.
Oral antifungal agents also work, but since this is not a harmful infection, most doctors prefer not to use an oral drug with more possible side effects. Perhaps one of these was the antibiotic given to you by your physician.
Treatment of T. versicolor can be frustrating since it usually recurs, due to reinfection from fungus elsewhere on the skin or on the scalp. Many people whom I see simply get used to treating it for a couple of weeks before each summer so that most of the unsightly blotching is prevented. Even when the condition is treated effectively, the untanned areas will not match the tanned skin around them until the person has had more sun exposure and tanning of the areas that were infected can occur.