Skin reactions to urine in patients with interstitial cystitis

Eight of 11 patients with interstitial cystitis had positive skin reactions to patch tests with urine (delayed type IV or irritant reactions). The positive reactions were seen to tests with the patients' own urine, but also, although less frequently, to tests with foreign urine as well. Immediate reactions (type I reactions; prick tests, scratch patch tests, and 20-minute patch tests) were not observed. The clinical morphology and the histology of the positive patch tests suggest a toxic rather than an allergic reaction, although the latter could not be totally excluded. The positive skin reactions may be relevant in the pathogenesis of interstitial cystitis suggesting a mucosal hyperreactivity to some component of urine.