Paraben esters are incorporated in most dermatologic and cosmetic creams and lotions as preservatives. A 2-year clinical study on the allergenic potential of these bacteriostatic and fungistatic chemicals showed that of 273 consecutive patients with chronic dermatitis who were routinely patch''tested to 5 % paraben in petrolatum had paraben allergy, an 0. 8 % incidence. Strongly positive patch test reactions in 4 patients with marked paraben allergy correlated well with the clinical course. Patients with contact dermatitis caused by paraben allergy present with long histories of intractable dermatitis which continues to flare regardless of the corticosteroid cream prescribed. Once the proper diagnosis is recognized and a paraben free medication is applied, these patients make a rapid and complete recovery. Paraben allergy must be suspected in any patient who gives a long history of recalcitrant dermatitis which has not responded to customary dermatologic diagnostic and therapeutic technique.