How are you? A boil, also referred to as a skin abscess, is a localized infection deep in the skin. A boil generally starts as a reddened, tender area. Over time, the area becomes firm and hard. When it "forms a head," then it can be surgically opened or spontaneously drained out through the surface of the skin.
One type is the Hidradenitis suppurativa. This is a condition in which there are multiple abscesses that form under the armpits and often in the groin area. These areas are a result of local inflammation of the sweat glands. This form of skin infection is difficult to treat with antibiotics alone and typically requires a surgical procedure to remove the involved sweat glands in order to stop the skin inflammation.
I hope this helps. Take care and keep us posted.