Anaphylaxis due to progesterone hypersensitivity: A rare cause of recurrent anaphylaxis.

Progesterone hypersensitivity (PH) is a rare but underrecognized cause of recurrent anaphylaxis in women, particularly those of reproductive age. Both endogenous and exogenous progesterone can trigger hypersensitivity reactions, with clinical presentations ranging from urticaria to life-threatening anaphylaxis. We report a case of a 33-year-old Vietnamese woman who experienced six episodes of unexplained anaphylaxis over two years. A thorough clinical history revealed exposure to intramuscular progesterone during in vitro fertilization cycles and cyclical vulvar skin eruptions before menstruation. Skin prick testing with injectable progesterone was negative, while intradermal testing produced a positive reaction, confirming the diagnosis of PH. The patient was thoroughly counseled regarding her condition and equipped with an epinephrine auto-injector alongside a written anaphylaxis action plan. Daily antihistamine therapy with levocetirizine was initiated to mitigate the risk of endogenous progesterone-induced reactions. Given her stable condition and sterilization history, no further hormonal intervention was required. During two years of follow-up, she remained asymptomatic, with no recurrence of anaphylaxis. This case highlights the importance of considering PH in the differential diagnosis of recurrent anaphylaxis in women, especially those with cyclical allergic symptoms or a history of exogenous progesterone exposure. Early recognition and appropriate management are crucial to prevent potentially life-threatening events.