Allergic contact dermatitis to propylene glycol in calcipotriene ointment.

A woman developed a pruritic exacerbation of her methotrexate-dependent psoriasis after applying topical calcipotriene ointment. Patch test reactions were positive to propylene glycol 1 percent and white petrolatum, but to none of the other ingredients of the medication. Physicians would be advised to patch test patients to both the therapeutic medication and the excipients of topical substances to which patients have adverse reactions. By so doing, an allergic reaction to one or more of the excipients may be found, thus the patient may be provided the benefit of the topical medication by using it in a form that does not contain the allergenic substance.