Allergic contact dermatitis is a condition that causes the skin to itch as a result of an allergic reaction to a material which comes in contact with the skin. The reaction does not occur immediately. Rather, it usually takes several hours to manifest itself. Provided that the skin does not come in contact with the material, it will die down over the ensuing days.
Allergic contact dermatitis should be differentiated from urticaria, which is a condition in which an immediate rash appears after skin contact with an allergen. In this case, the rash will disappear quickly, sometimes within minutes, but always within hours. In cases of allergic contact dermatitis, the reaction, generally, is confined to the contaminated area. Severe cases have been known to extend outside the contact area.