Eczema, also known as atopic dermatitis in its extreme form, is an itchy rash that occurs on the hands, arms, legs, and neck, but can cover the entire body in extreme cases. It is non-contagious. Atopic dermatitis is frequently caused by allergens. Prolonged exposure to the allergens may aggravate the itchy rash and cause additional discomfort.
National Institute of Allergy and Infectious Diseases