Feline Chin Acne and Eosinophilic Complex

Good to connect on this case. It's a classic feline presentation, and you're right to think of these as two manifestations of one underlying problem, which is almost certainly allergic in nature. My approach is to manage the active lesions while simultaneously starting the workup for the trigger.

1. Immediate Lesion Management:

Chin Acne: Start with cytology of the chin. You need to know if you're dealing with a secondary bacterial or Malassezia* component. For topical therapy, I'd recommend twice-daily application of mupirocin 2% ointment to the affected areas if cocci are present. Alternatively, a chlorhexidine/miconazole mousse or wipe is excellent for managing mixed infections and is often better tolerated by cats than a full shampoo. I'd also ensure the owner is using ceramic or stainless steel bowls, cleaned daily.
* Eosinophilic Granuloma Complex (EGC): For the indolent ulcer, a short, tapering course of oral prednisolone (1-2 mg/kg/day) is my preferred starting point for rapid control. It will reduce the inflammation and discomfort quickly while you begin the diagnostic workup. Cyclosporine (7 mg/kg/day) is an excellent steroid-sparing option and my choice for long-term management, but it can take 4-6 weeks for full effect. I typically use prednisolone to induce remission, then taper off as the cyclosporine kicks in if chronic therapy is needed.

2. The Underlying Allergy Workup (Start this now):

The goal is to find the trigger so you can minimize long-term immunosuppression.

* Flea Control: This is non-negotiable. Ensure the cat and all other pets in the household are on a modern, effective flea preventive (e.g., a topical isoxazoline). Flea allergy is a primary trigger for both EGC and head/neck pruritus in cats.
* Elimination Diet Trial: Concurrently with flea control, I would initiate a strict 8-10 week elimination diet trial with either a novel protein (e.g., venison, rabbit) or a hydrolyzed protein diet. This is the only way to rule out a cutaneous adverse food reaction. Stress to the owner that absolutely nothing else can be fed during this time.

My plan would be to start the diet trial and strict flea control immediately while using a 3-4 week tapering course of prednisolone to manage the EGC. By the time the steroid taper is complete, you'll be well into the diet trial and can assess the response to that alone. If lesions recur after the steroids are stopped despite the diet, you're likely dealing with atopic dermatitis, and long-term cyclosporine would be the next logical step.