I'm sorry to hear of this with your dog. There appears to be two different disorders to consider. The chronic ear pruritis (itchiness) and accumulation of cerumen (wax) is characteristic of reactive otitis - ear that become inflamed and secondarily infected with both yeast (Malassezia) and bacteria secondary to an allergic dermatitis - atopy* (allergies to environmental allergens such as pollens, molds, dust, and dust mites, etc.) is most common and food intolerance** should be another consideration.
The draining blisters are likely to represent canine pedal furunculosis in the American bulldog. The etiopathogenesis of this skin disorder is unclear but one hypothesis is that sterile pedal furunculosis is a persistent, immune-mediated, inflammatory response to keratin and triglycerides liberated from ruptured hair follicles, sebaceous glands, and the panniculus (fatty layer of the skin). Here's a synopsis of this disorder for you:
1) The clinician should make sure that the initiating cause of the furunculosis (e.g., atopy, food allergy, wet environment, dirt kennels, friction in short-coated breeds) has been identified and corrected if possible.
2) If draining lesions are secondarily infected, appropriate antibiotics or antifungal medications should be administered for a minimum of 4-6 weeks.
3) For solitary lesions, surgical excision or laser ablation may be curative. I understand that you want to avoid more surgeries, however.
4) Cleansing wipes (alcohol-free acne pads, baby wipes, chlorhexidine-containing pledgets, or other antimicrobial wipes used every 12-72 hours work very well. For developing bullae, topical dimethy sulfoxide (DMSO) combined with the antibiotic enrofloxacin (to make a 10 mg/mL solution) and steroid (dexamethasone or fluocinolone) should be applied every 12-72 hours until lesions resolve. To prevent recurrence, the feet should be wiped or scrubbed in the direction of hair growth to remove any "ingrown" hairs.
5) Alternatively, treatment with combination tetracycline and niacinamide may be effective in some dogs. Please discuss this option with his vet. Anecdotal reports suggest that doxycycline can be administered every 12 hours until response occurs, then tapered to the lowest effective dose or doxycycline may be substituted for tetracycline.
6) Anecdotal reports suggest that treatment with cyclosporine may be effective in some dogs.
7) For severe, nonsurgical, or multiple lesions, treatment with glucocorticosteroids such as prednisone may be effective.
Finally, consider having him see a specialist veterinary dermatologist if you wish. Please see here: www.acvd.org. Such a specialist will know of the very latest approaches to this vexing disorder - approaches that haven't yet reached the veterinary literature.
*Environmental allergies (atopy) are usually initially addressed with a glucocorticosteroid such as prednisone. In some dogs an over the counter antihistamine such as clemastine (Tavist) at a dose of 0.025 - 0.75mg/lb twice daily or diphenhydramine (Benadryl) dosed at 1-2mg/lb twice daily (maximum dose of 50 mg at any one time) may be effective. Antihistamines, however, aren’t reliably effective. Adding fish oil to the diet at a dose of 20mg/lb daily of the EPA in the fish oil might synergize with antihistamines to provide better anti-pruritic action. The omega-3 fatty acids in fish oil are antiinflammatory but may take 8-12 weeks to kick in. The new cytokine antagonist oclacitinib (Apoquel) is likely to revolutionize how we address atopic dogs and should be discussed with his vet. Oclacitinib works as well as a steroid without a steroid's adverse effects. Please note that atopy, at least initially, should have a seasonality to it while a food intolerance should cause pruritis regardless of the season. Chronically atopic dogs may be pruritic year round.
**Food intolerance/allergy is addressed with prescription hypoallergenic diets. These special foods contain just one novel (rabbit, duck, e.g.) animal protein or proteins that have been chemically altered (hydrolyzed) to the point that his immune system doesn't "see" anything to be allergic to. The over the counter hypoallergenic foods too often contain proteins not listed on the label - soy is a common one - and these proteins would confound our evaluation of the efficacy of the hypoallergenic diet. The prescription foods are available from his vet. There are many novel protein foods and a prototypical hydrolyzed protein food is Hill’s Prescription Diet z/d ultra. (I prefer the hydrolyzed protein diets because it avoids the possibility of my patient being intolerant to even a novel protein.) A positive response is usually seen within a few weeks if we’ve eliminated the offending food allergen. Food intolerance can arise at any age and even after our patient has been eating the same food for quite some time.
Please respond with further questions or concerns if you wish.