Intradermal testing for autoimmune progesterone dermatitis: should we be basing the diagnosis on it?

Autoimmune progesterone dermatitis (APD) is a rare skin disorder with varying presentations, resulting from hypersensitivity to endogenous progesterone during the luteal phase of the menstrual cycle. The diagnosis has been traditionally confirmed with intradermal progesterone testing (IPT) or intramuscular challenge with progesterone or its derivatives. We present a case of a 31-year-old woman with suspected APD who underwent IPT to progesterone. The patient's cyclical symptoms, positive skin reaction and symptoms following IPT were sufficient to make a diagnosis of APD. However, we also tested 10 healthy female controls without symptoms of APD, and found that 9 of these also developed positive skin reactions to intradermal progesterone at 15 min, 24 and 48 h, albeit to a lesser extent. Therefore, these results raise doubts about the validity of using IPT to make a diagnosis of APD. Further research on appropriate testing is needed.