We studied the pharmacokinetics and antipruritic effects of hydroxyzine hydrochloride in 12 children, mean age 6.1 +/- 4.6 years, with severe atopic dermatitis. After a single 0.7 mg/kg orally administered dose of the drug, the mean peak serum hydroxyzine concentration of 47.4 +/- 17.3 ng/ml occurred at a mean time of 2.0 +/- 0.9 hours. The mean elimination half-life was 7.1 +/- 2.3 hours, the mean clearance rate was 32.08 +/- 11.05 ml/min/kg, and the mean apparent volume of distribution was 18.5 +/- 8.6 L/kg. The elimination half-life increased with increasing age (r = 0.83). Pruritus was significantly suppressed from 1 to 24 hours after the administration of the dose, with greater than 85% suppression from 2 to 12 hours. The only adverse effect reported was sedation. In a subsequent double-blind, crossover, multiple-dose study of 2 weeks' duration, hydroxyzine 0.7 mg/kg three times daily was as effective as hydroxyzine 1.4 mg/kg three times daily in relieving pruritus and promoting resolution of the skin lesions. The 0.7 mg/kg tid dose caused significantly less sedation than the 1.4 mg/kg tid dose.