Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 15 years of experience. I look forward to working with you.
This does sound suspicious to be related to allergies, but if it is bleeding and is a slightly raised pink plaque then this may be an esoinophilic granuloma plaque (here is a site for more information: (http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=656 ). These plaques usually require corticosteroids (injectable or oral) to clear. And they are related to an underlying allergy.
It is important to understand with cat allergies that our top three allergic skin diseases are flea allergy dermatitis, food allergy dermatitis and atopic dermatitis (environmental allergy). We can easily control the first and even if Runty is indoors only with very sensitive skin he must be on a monthly flea control product that is effective such as one from your vet (like Advantage multi or Revolution) or the only one over-the-counter I would trust is Advantage. Frontline and its knock-off fipronil-containing products no longer work well in this country for fleas in cats. :(
For food allergy, most of the time the crusting/scabbing is around the head. A food trial is needed to try to determine if this is the problem. A food trial is not something you do on your own with an over-the-counter diet, but you must feed a prescription hypoallergenic diet as prescribed by your vet. Right now the hydrolyzed diets (Hill's z/d or Royal Canine Hydrolyzed or Purina HA) are the diets of choice. We feed this diet exclusively (no treats or foods outside the diet) for 8 to 12 weeks. At that time was are also resolving the skin irritations
and infections. If there is no relpase and all goes away, then this may be food allergy.
After this we must then ask if we think this could be atopic dermatitis OR if this could be immune-mediated disease like pemphigus. At that point based on responses to medications your vet may be able to know. To diagnose an immune-mediated disease will require a skin biopsy be performed and submitted to a dermatopathologist. For environmental allergies, allergy testing (intraderma or serum/blood testing) will be needed and then you have the choice of immune therapy (allergy shots) or starting a longer term medication like atopica to control the problem.
Okay, I have thrown a lot of information your way. The next step is to talk to your vet and start to work through this problem. If your vet seems unable to help, then either seek out a second opinion or ask to be referred to your closest veterinary dermatologist for consultation.
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