Caffeine as an adjunct in the treatment of atopic dermatitis.

To the Editor. — Kaplan et al (Archives114:60-62, 1978) reported that caffeine produces beneficial effects when used topically with hydrocortisone in the treatment of atopic dermatitis. The authors suggest as the mode of action that caffeine inhibits the enzyme phosphodiesterase, thereby increasing the levels of cyclic adenosine-3′, 5′-monophosphate (cAMP) in the skin, which apparently is responsible for alleviating the symptoms of atopic dermatitis. We believe that if enzyme inhibition is a factor, its role is a minor one, since generally enzyme inhibitors are effective at low concentration levels. In their study, Kaplan et al used 30% caffeine and 0.5% hydrocortisone in hydrophilic ointment. Since 30% caffeine is an enormous quantity of drug to which to attribute enzyme inhibition as its