Does your cat have a perpetually dirty chin like the one above? This is a mild case of feline acne caused by overactive sebaceous glands.
It starts as greasiness of the fur and black flecks in light-coloured hair. In some cats it progresses to swelling, inflammation and infection, like pimples in humans.
In mild cases, changing food and water bowls from plastic to ceramic, and washing them in the dishwasher after use will clear it up. Use chlorhexidine wash or wipes to clean the chin.
In more severe cases like the one below, your vet will check for secondary infections with bacteria, mites and fungi, and treat accordingly. Sometimes the cat needs pain relief, too.