Underarm boils occur when bacteria or fungi that is naturally found on the skin makes its way into a hair follicle, infecting both the follicle and surrounding tissues, explains MedlinePlus. When a boil first develops, it presents as a swelling on the skin that gradually becomes filled with pus
Risk factors that can increase an individual's risk of developing boils include inadequate hygiene, medical conditions such as diabetes or immune disorders, chemical exposures and poor diet, explains WebMD. When a boil becomes infected, it may become swollen and feel warm to the touch. Additional signs of infection include swollen glands, fever and the development of additional boils.
In many cases, underarm boils can be treated at home with warm compresses, as the heat can help to minimize pain and encourage drainage of pus, according to Mayo Clinic. Larger boils may require medical drainage procedures in which a physician creates an opening to begin the drainage process. Severe infections or boils that tend to recur may also be treated with antibiotics. To minimize the risk of contamination, it is important for individuals with boils to wash their hands immediately after touching affected areas and wash all fabrics that come in contact with the skin.