Contact dermatitis is localised inflammation of the skin that results from contact with an external substance. This external substance can be an irritant (irritant contact dermatitis) or an allergen (allergic contact dermatitis).
Contact dermatitis results in large, burning, and itchy rashes that may take several days or weeks to heal. Chronic contact dermatitis can develop when the removal of the offending agent (irritant or allergen) no longer provides the expected relief. In 2004, there were an estimated 72 million people with contact dermatitis in the US.