Skin rash from tri top

I've had this issue with a few run tops and even some work clothes--probably related to heat/humidity here as well as sentsitive skin. If it's only happening in one place it is probably from friction rather than an allergic reaction, so an antihistamine won't do much good. At any rate, it's probably safer to just go ahead and get a rash once a in while than to mess with antihistammines before a race, unless itching is driving you crazy during the race. If the trouble area is small, would a waterproof bandaid or something work? I've worn them and had them stay on for a sprint tri under my suit (over road rash that I didn't want to rub or to get salt water in). The other thing would be to get the top off as soon as possible after the race and get into something clean and dry.

If it is actually allergy related (which I doubt, because it would probably affect a larger area), you might look into what you are using to wash the tri top. Lots of people use special sports washes or liquid soap for delicates and if it's a product you're not used to, maybe you're allergic to it and that area just happens to be where you have more contact or more sensitive skin. There are a few detergent products sold here in Asia that I have to avoid because when I wash clothes in them, it makes me itch, especially in hot, humid weather (which is pretty much all the time). I have really sensitive skin, though (allergic to lots of soaps, makeup products, and sunscreens) so this is probably not that common.