The, "Prince Melon", a sort of honey dew, is intensively cultivated in the Kumamoto district. We found a patient who was involved in the cultivations of the melons and who had suffered from asthmatic attacks every spring season for 7 years. The season when the attacks took place was coincident with the melon-harvest time but not the flowering season. Antigen extraction was performed from the hair-like substances of the melon skin. Skin test threshold of the patient was 10^<-10> dilution. Provocation test was positive. RAST value of the patient's serum was extremely high, and the value was markedly lowered by preincubation of the serum with uncoupled original antigen. Rabbit antiserum to the melon extract showed 2 precipitating lines to the antigen by agar immunodiffusion. Results of routine skin test including the melon to all the other patients who visited our clinic indicated relative coincidence of the positive skin test to the melon and mite antigen. However, by the melon RAST inhibition test and agar immunodiffusion test with the mite, no inhibition or cross-reactivity was observed. The results show that the asthmatic attacks were provoked by Type I allergy of inhaled melon skin substance. Cross-reactivity among the "Prince Melon", watermelon, and muskmelon was observed by agar immunodiffusion, skin test and RAST inhibition test.
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