Hidradenitis suppurativa (HS) is a disorder in which swollen, tender, boil-like lesions develop in the armpits, groin and other areas of body, due to the inflammation of apocrine sweat glands. Apocrine glands are located primarily in the underarms and in the areas surrounding the anus, breasts and genitals. Over time, lesions may become infected (abscess) and repeatedly drain and fill with pus.

An HS lesion appears when perspiration has not drained properly and accumulates in hair follicles. Over time, this trapped perspiration eventually causes the nearby apocrine sweat gland to burst, forcing new perspiration and bacteria into adjacent tissue and often causing additional pus-filled lesions to appear.

Left untreated, lesions may become connected to one another beneath the skin or remain isolated as painful and inflamed masses that are firm and sensitive to touch. The condition is chronic but not contagious.

The disorder usually occurs in adults who are otherwise healthy. It rarely begins before puberty or after menopause. Although the cause is unknown, the condition has a number of risk factors, including medical history, excessive sweating (hyperhidrosis), obesity and certain lifestyle factors (e.g., smoking). HS is often associated with certain other disorders, such as Crohn's disease, irritable bowel syndrome and some forms of arthritis. HS can also occur without association to any risk factor or condition.

Diagnosis of HS involves a physician taking a patient’s medical history and performing a physical examination. Additional testing may be performed (e.g., blood tests) to aid in diagnosis, but is not always necessary. HS is generally categorized into three stages, with treatment becoming less effective as the disease progresses. Early diagnosis is important because most cases of early stage HS can be effectively treated.

Medication (e.g., antibiotics, retinoids, corticosteroids) is typically recommended for the treatment of early stages of HS, whereas surgery is often performed to treat advanced stages of the disease. Combination therapy may also be used in some patients.

Because HS occurs without a known cause, it is impossible to prevent lesions from developing. However, taking certain steps, such as avoiding smoking, practicing proper hygiene and maintaining a healthy weight, may reduce the chance of lesions appearing.