I'm sorry to hear that your Chihuahua is having this issue. Itching as he is can indicate several things. Thyroid problems, allergies (food, fleas etc can all be culprits) and fungal infections are some of the main culprits. The blackness of his skin could likely be due to a fungal infection. It's important to have him into your vet for a skin scraping so that this can be pinpointed (some immune system issues can cause this as well). If a fungal infection is present, they will likely put him on a oral antifungal. You can use a soothing oatmeal shampoo and a product such as Derma Pet on the area for now. Keeping him on an all natural kibble and adding 1 T of plain yogurt to it daily may help as well. I hope he's feeling better soon.
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