Considered a severe form of acne, hidradenitis suppurativa is a chronic skin inflammation that usually occurs deep in the skin in areas of the body with sweat glands, such as the groin or armpits. It is characterized by a combination of blackheads and red lesions that break open and drain pus, which may cause itching or sweating. As the red bumps grow in size, they can become more painful.

Hidradenitis suppurativa occurs when oil glands and hair follicles become blocked with sweat gland fluid, dead skin cells and other elements found in hair follicles. These substances become trapped and push out into the surrounding tissue. A break or cut of the skin then allows bacteria to enter the area and cause the inflammation.