Feline acne develops in the sebaceous glands on the underside of the chin and edges of the lips. Blockage of skin pores by excess sebum or keratin is a predisposing cause. It is more common in cats with oily skin. It is not analogous to acne in people.
Feline acne is identified by finding blackheads or pimplelike bumps that come to a head and drain pus. Swelling of the entire chin and lower lips may be seen in severe cases.
Your feline will look (and feel!) like the cat’s meow after a good grooming session.
By nature, cats are extremely fastidious. You’ve no doubt watched your kitty washing herself several times a day. For the most part she can take care of herself very well, thank you, but sometimes she’ll need a little help from you.
A similar condition can be caused by an allergic reaction to rubber or plastic food and water bowls. In those cases, simply changing to stainless steel or ceramic dishes will clear up the condition.
Treatment: The infection usually responds to cleansing of the skin twice a day with an ointment or gel containing 2.5 to 5 percent benzoyl peroxide (OxyDex), chlorhexidine (Nolvasan) or povidone-iodine (Betadine). When excess sebum is a factor, the skin should be cleansed with a medicated shampoo for cats. An extensive or deep infection may require antibiotics. Because the underlying problem remains the same, acne often recurs when treatment is stopped. Some cats do better if switched from a wet to a dry food, or if the owner cleans their chin after every meal.
WebMD Veterinary Reference from "Cat Owner's Home Veterinary Handbook"