A cyst and a boil can both look like a bump, though their causes differ. For example: A boil—also known as a furuncle—occurs due to a bacterial infection of a hair follicle and the tissue around it.

Boils and cysts are two types of growths on the body. Also known as furuncles, boils are pockets of pus (a creamy, white substance) on the skin caused by bacteria infecting hair follicles.

That tender, angry bump in your armpit started as a tiny annoyance. Now it’s a throbbing, painful mess that makes putting on deodorant feel like torture. If you’ve dealt with armpit boils, you know ...