It's always best to check with the vet regarding using products like peroxide or tea trea oil on a pet. They may be safe, which is great, but they would know concentrations and application methods which would be best.
There is just too much out there that can harm a pet. And what works safely on one animal, doesn't always have the same results on another. Always check with a vet first. They don't mind a quick phone call with a question now and then.
:) :)