An allergic reaction by a cat to rubber or plastic bowls for water or food is a similar condition to feline acne which is identified by seeing blackheads or pimple-like bumps that come to a head. In severe cases the entire chin and lower lips may swell up.
Where and How
Cat acne develops in the sebaceous glands on the undersides of the chin and also on the edges of the cat’s lips. A cat can be predisposed to feline acne if the skin pores are blocked up by an excess of keratin or sebum. Cats with an oily skin more commonly have feline acne. It is similar to human acne.
Home Treatment
A home treatment for cat acne would be to (1) change food and water bowls to ceramic or stainless steel dishes and (2) an infection normally responds to cleaning the area twice a day with an ointment containing 2.5 to 5% benzoyl peroxide (in America this is OxyDex and see below), or chlorhexidine (Nolvasan) or povidone-iodine (Betadine).
Shampoo and Antibiotics
If the condition is caused by an excess of sebum or it is a factor in the condition, the skin should be cleaned with a medicated shampoo for cats. If the infection is extensive or severe, antibiotics may be required and a prescription from a veterinarian is needed.
Reappearance
Once the treatment is stopped the underlying problem may take hold causing the acne to reappear.
It is suggested that some cats might improve if fed dry cat food (as opposed to wet) and/or the cat’s owner cleans their cat’s chin after every meal. We cat food is generally seen as better for cat health as it more accurately replicates cat prey in terms of ingredients.
Source
These recommendations come from a well-respected work on home treatments for domestic cats, namely, Cat Owner’s Home Veterinary Handbook, Third Edition.