Dermatitis is a general term to describe any inflammation of the skin. It is generally characterized by a rash but can also be characterized by bumps, itching and blisters. The "horse" cause of dermatitis is a reaction to an irritant, and is often an allergic reaction. Less common causes are dry skin, celiac disease, and infection. Ironically, soap and detergent are the most common irritants that lead to dermatitis.