Atopic dermatitis is a common, often persistent skin disease that affects a large percentage of the world's population. Atopy is a special type of allergic hypersensitivity that is associated with asthma, inhalant allergies (hay fever), and a chronic dermatitis. There is a known hereditary component of the disease, and it is more common in affected families. Criteria that enable a doctor to diagnose it include the typical appearance and distribution of the rash in a patient with a personal or family history of asthma and/or hay fever. The term atopic is from the Greek meaning "strange." The term dermatitis means inflammation of the skin. Many physicians and patients use the term eczema when they are referring to this condition. Sometimes it is called neurodermatitis. In atopic dermatitis, the skin becomes extremely itchy and inflamed, causing redness, swelling, vesicle formation (minute blisters), cracking, weeping, crusting, and scaling. This type of eruption is termed eczematous. In addition, dry skin is a very common complaint in almost all those afflicted with atopic dermatitis.