Chin acne in cats is known by several different names: feline acne, chin folliculitis and chin furunculosis
What is chin acne?
It's a disorder of follicular keratinisation – which means that the hair follicle cells don't just shed away like they're supposed to and instead they stick around and cause blockages. Why this happens is still unknown. Plenty of theories have been proposed including poor grooming habits, abnormal sebum production, stress, localised skin defects, viral infections, immunosuppression, and various allergies/irritants. None of these has been proven.
Who gets chin acne?
It can occur in cats of any age, breed or sex. It's not a disease of adolescence like acne in people (and dogs).
What are the signs?
The main sign is the presence of comedones – these are like blackheads (small dark bumps that contain thick material). Most cats with these don't seem bothered by them at all (ie they are asymptomatic). However, the comedones can become pustular if a secondary bacterial infection occurs. Sometimes, there can be lots of oozing/crusty lesions with swelling and redness of the whole chin area, this may be quite painful.
To see some images, go this Science Direct article: Chapter 12 - Keratinization and Seborrheic Disorders
How is chin acne treated?
This depends on the severity. If your cat has asymptomatic comedones, you probably don't need to treat at all. If there is a secondary infection, this will likely require some sort of therapy.
There are a couple of treatment approaches.
Topical – the most commonly used topical treatments are washes/shampoos that contain active ingredients such as benzoyl peroxide and salicylic acid. These are used every 12–24 hours until the problem resolves (which can be really challenging as cats typically hate their chins being washed). Topical antibacterials can be used too if symptoms are mild. Anything containing an antibiotic will be prescription only, so your vet would need to see your cat. Some people have success using warm compresses that contain magnesium sulphate (Epsom salts) – mix 2 tablespoons into a litre of warm water, soak a face washer and hold it against the area for a few minutes to soften the comedones and promote drainage. Clipping fur away from the chin tends to help with topical treatment
Systemic – this generally means giving antibiotics for secondary bacterial infection. In some cases, we may need to also give anti-inflammatory medication.
What's the prognosis?
Again, this depends on severity. Many if not most cats experience persistence or recurrence of comedones. Regular washing can help reduce recurrence. With severe cases, there can be considerable scarring and cyst formation.