Hidradenitis suppurativa (HS) causes you to get painful bumps under your skin in the hair roots near some of your sweat glands. There's no cure, but treatments and lifestyle changes can bring some relief and cut down on flare-ups.
Most experts think they’re caused by blockages in the hair roots. They usually happen in areas where you have hair, such as under your arms, in the groin, and between the buttocks, but you can also get outbreaks in places where your skin rubs together, such as between your thighs or, for women, under the breasts.
The bumps can get infected. When that happens, pockets form under the skin and fill with pus that can smell bad when they break open. They can leave scars, too. To keep new bumps from forming, get treatment as soon as you can.