The 2 most common types of cysts we treat in the office are epidermal inclusion cysts (EIC) and milia. EICs are keratin-filled sacs that present as bumps on the skin (from a few millimeters to several centimeters in size), usually with a blackhead-like dot in the center. They contain keratin (a cheesy substance), not sebum, so they are very commonly erroneously referred to as sebaceous cysts, which is a misnomer. EICs appear sporadically, for no particular reason, sometimes due to a genetic predisposition. Smoking can make them more likely to occur.