Hidradenitis suppurativa (HS), also known as acne inversa, is a long-term auto-inflammatory disease characterized by the occurrence of inflamed and swollen lumps. These are typically painful and break open, releasing fluid or pus. The areas most commonly affected are the underarms, under the breasts, and the groin. Scar tissue remains after healing.The exact cause is usually unclear but believed to involve a combination of genetic and environmental factors. About a third of people with the disease have an affected family member. Other risk factors include obesity and smoking. The condition is not caused by an infection, poor hygiene, or the use of deodorant. Instead, it is believed to be caused by hair follicles that are near apocrine sweat glands being blocked, which in turn causes inflammation in the sweat glands. Diagnosis is based on the symptoms.There is no known cure. Warm baths may be tried in those with mild disease. Cutting open the lesions to allow them to drain does not result in significant benefit. While antibiotics are commonly used, evidence for their use is poor. Immunosuppressive medication may also be tried. In those with more severe disease, laser therapy or surgery to remove the affected skin may be carried out. Rarely, a skin lesion may develop into skin cancer.If mild cases of HS are included, then the estimate of its frequency is from one to four percent of the population. Women are three times more likely to be diagnosed with it than men. Onset is typically in young adulthood and may become less common after fifty years old. It was first described some time between 1833 and 1839 by French anatomist Alfred Velpeau.