Hello,
It can be due to boils, folliculitis or erythema induratum (less likely). Boils are caused by infection of the hair follicle by
staph aureus. Hair follicles that are blocked by greasy creams, petroleum jelly, or similar products are more vulnerable to infection. Bacterial skin infections can be spread by shared cosmetics or washcloths, close human contact, or by contact with pus from a boil or carbuncle. Treatment includes antibiotics and do not touch or pick them up.