['Dimethyl sulfoxide (DMSO), an agent that provides symptomatic relief in patients with interstitial cystitis (IC) works via an unknown mechanism. We investigated whether DMSO acts as a chemical stimulant of mast cell degranulation.', 'A radioimmunoassay (RIA) specific for histamine was used to test this hypothesis. Twelve women with strictly diagnosed IC were treated with intravesical instillations of DMSO. Treatments were repeated at varying intervals, and each patient received three to six treatments. Urine histamine levels were measured before and after each intravesical instillation of DMSO. Dilutional effects of DMSO were corrected for by conversion of urine histamine concentration to urine histamine:creatinine ratio.', 'The RIA was unaffected by the addition of DMSO to urine. No consistent change in the urine histamine:creatinine ratio following DMSO instillation was found. Trend analysis revealed no trend in the histamine:creatinine ratio with time.'] Does dimethyl sulfoxide trigger urine histamine release in interstitial cystitis?