I'm sorry to hear of this with Tutu. I understand your frustration and financial constraints. I don't know everything you've tried so I'm going to post my complete synopsis of how generalized yeast infection (malasseziasis) is addressed. Pleast note that the only over the counter products of value are the shampoos I've mentioned. They can be found in pet/feed stores or at Tutu's vet hospital or online.
1. Any underlying cause (allergies/food intolerance, atopy, e.g., endocrinopathy/hypothyroidism, e.g., keratinization defect/seborrhea) must be identified and corrected.
2. For mild cases, topical therapy alone is often effective. The patient should be bathed every 2-3 days with shampoo that contains 2% ketoconazole, 1% ketoconazole/2% chlorhexidine (https://www.amazon.com/Keto-C-Ketoconazole-1-Chlorhexidine-Shampoo/dp/B00Q34IY6Y), 2% miconazole, 2-4% chlorhexidine, or 1% selenium sulfide (Selsun Blue). Shampoos that have two active ingredients provide better efficacy. Treatment should be continued until the lesions resolve and follow-up skin cytology reveals no organisms (approximately 4 weeks).
3. The treatment of choice for moderate to severe cases is ketoconazole or fluconazole 10 mg/kg orally with food every 24 hours. Treatment should be continued until lesions resolve and follow-up skin cytology reveals no organisms (approximately 4 weeks).
4. Alternatively, treatment with terbinafine 5-40 mg/kg orally every 24 hours or itraconazole (Sporanox) 5-10 mg/kg every 24 hours for 4 weeks may be effective.
The prognosis is good if the underlying cause can be identifed and corrected. Otherwise, regular once- or twice-weekly antiyeast shampoo baths may be needed to prevent relapse. Please respond with further questions or concerns if you wish.