A case of type IV solar urticaria identified by reverse in vitro serum test.

We had a 17-year-old male patient with solar urticaria diagnosed as type IV of modified Harber's classification. The action spectrum of this case was estimated to be 433-499 nm and the inhibition spectrum was 533 nm. Both in vitro serum test and tentatively designated "reverse in vitro serum test" were positive. The patient was prescribed 20 mg/day epinastine hydrochloride (Alesion) orally for 49 weeks with improvement of the symptoms.