Boils form on the buttocks when bacteria enters the skin through minor abrasions and makes its way into the hair follicles or oil glands, creating an infection, explains WebMD. Boils first present as hard, inflamed swellings that gradually soften and fill with white pus.
Boils commonly develop on the buttocks due to the fact that the area contains hair and is prone to friction and sweating, according to Mayo Clinic. In certain cases, boils can grow up to the size of a baseball if the area fills with excess pus. Over time, the tip of the boil bursts, causing the fluid to drain out.
As boils drain, the area may weep and become crusted over, explains MedlinePlus. The infection may also spread, causing additional boils to form. In many cases, boils require surgical drainage, but certain boil infections may drain spontaneously without the need for treatment. To treat boils at home, sufferers should apply warm water compresses to the affected area to encourage spontaneous draining. It is important to avoid squeezing the boil, as this can lead to further infection. Individuals with boils should seek medical treatment if the infections do not resolve within two weeks or if the boil is located on the spine or on the center of the face.