A boil is a skin infection that starts in a hair follicle. It is caused by bacteria that enter the follicle and begin to multiply. As the bacteria multiply, they produce pus, which causes the follicle to swell and become inflamed. Boils can be painful and tender to the touch. They can also cause redness, swelling, and drainage of pus.
Boils are most commonly caused by the bacteria Staphylococcus aureus. This bacteria is found on the skin of many healthy people. However, it can cause an infection if it enters a hair follicle that is damaged or irritated. Boils can also be caused by other types of bacteria, such as Streptococcus pyogenes and Pseudomonas aeruginosa.
