Systemic sensitization to 17 beta-oestradiol via the transdermal therapeutic system.

Introduction. Transdermal administration of drugs to obtain a systemic effect may lead to allergic sensitization and compromise subsequent use via another administration route. Observation. A 52-year-old woman presented contact eczema with the transdermal therapeutic system Estraderm TTS50(R). Generalized eczema developed later after oral administration of an oestrogen derivative. Skin tests demonstrated allergic sensitization to 17 beta-oestradiol. Discussion. Contact eczema due to transdermal therapeutic systems are usually caused by agents other than the active drug. Sensitization to the active drug raises the risk of generalized eczema and subsequent systemic complications. This risk must be taken into account when prescribing substitution hormone therapy for menopause.