Smudge had really bad chin acne, but it wasn't getting worse, so I didn't ask the vet about it. But when she suggested I give him chlorpheniramine maleate for his allergic dermatitis, it really helped with his chin as well. Pretty much cleared up his constipation too, but if your cat tends in the other direction - well, you'll want to ask your vet anyway! The trick was finding food smelly enough to cover it that was also low enough in magnesium, as Smudge is the classic Unpillable Cat. But he really enjoys Triumph Beef/Tuna/Chicken twice a day, and his c/d kibble the rest of the time. I grind up a third of a pill (supposed to be 1 mg, a quarter of a pill, but he seldom finishes off all his wet food) in a mortar & pestle, dissolve in a little bit of water, and mash it into his wet food. His face & neck have all healed up except one tiny bit between his eyes, and he's more handsome than ever!