Which comes first: the itch or the rash? Atopic dermatitis is an "itch that rashes." If there is no scratching there is no eruption. Itching can be paroxysmal and severe. In most patients, itching is most severe in the evenings. Scratching frenzies may be reported. According to the U.K. Working Party, the diagnostic criteria for atopic dermatitis include:

• an itchy skin eruption
• plus three of the five following criteria:
  • History of flexural involvement: folds of the elbows, behind the knees, front of the ankles, or around the neck, and including cheeks in children less than 10 years.
  • A personal history of asthma or allergic rhinitis or a history of atopic disease (eczema (skin), allergic rhinitis (nose) or asthma in a first-degree relative in children under 10 years.
  • A history of generalized dry skin the last year.
  • Visible flexural eczema or eczema involving the cheeks, forehead, and outer limbs in children under 4 years.
  • Onset under the age of 2 years for patients that are more than 4 years of age.