Oh yes of course if not diluted correctly it could be bad! But if the natural rainwater dilution was bad then all chameleons (and other animals) would be dead.

I’m a little bit of an unorthodox person and I practice more holistic healing in my house so it’s just what I would do, but you don’t have to, I just feel like if there’s nothing more the vet can do then why not try as long as it’s done safely. Here’s some info if you decide to try..
https://www.the-natural-path.com/hydrogen-peroxide-therapy.html