Allergic contact dermatitis (ACD) is an itchy, red rash that you get from something that is contacting your skin.
The hands and the face are the two parts of the body that most commonly get ACD. On the hands, the main causes are soaps, moisturizers or rubber gloves. On the face, the common causes are shampoo and conditioner (rinsing down over your face - they usually don't cause any itching or rash on the scalp), soaps and moisturizers.
You can get it almost anywhere on the body, though - the neck, the arms, the legs, the chest, stomach, or back, or even the feet.
It can be really hard, almost impossible, to figure out what it causing it because most products contain similar ingredients (i.e. most shampoos have very similar ingredients to other shampoos, same goes for soaps, moisturizers, etc), so even if you suspect something is causing your rash, you may change products thinking it would get better if that product was causing it, but if the product has similar ingredients as the one you stopped using, you won't get any better.
If you think you might have contact dermatitis, give us a call at Bexley Dermatology Research to find out if you might qualify for any studies we have going on. In clinical research studies there is not cost for treatment and people who participate in them are usually compensated (paid!) for being treated in the study.