A healthy 33-year-old woman consumed a slimming product containing a mixture of herbal remedies without seeking medical advice. Two months later, the patient had hemorrhagic cystitis and discontinued the herbal product. Symptoms spontaneously remitted in a few days. Four months later, she took the same herbal remedy and the hemorrhagic cystitis reappeared. She then consulted her general practitioner. A urine culture test was negative, and the patient was advised to discontinue the herb intake. Again, the cystitis resolved within a week. The product involved contains a mixture of herbs, some of which have been associated with adverse effects that might account for the symptoms reported in this case.