Hydrogen peroxide therapies have been safely used for decades by many health care practitioners for a variety of reasons.
Sushi got intravenous hydrogen peroxide therapy which put her ME/CFS into remission for 2 years. But it also caused permanent damage to the veins, and it's hard for her to get blood drawn as a result. That does not seem like a particularly safe treatment, even if it did offer benefits. I would not trust H2O2 practitioners to conduct the necessary safety testing, as for one thing, such testing costs a lot of money.
But here we are not talking even about intravenous H2O2, we are talking about breathing H2O2 into the lungs, which is a different thing, and would have to be separately tested for safety. And in particular, would have to be tested for safety in COVID-19 patients, to ensure that they are not made worse.
It's possible H2O2 might have some benefits for COVID-19, but it's also possible it might be harmful.
Breathing in H2O2 is fringe, I've seen very few people do it when searching online. And H2O2 comes under the chemical category of a
peroxide-based bleach, so you are breathing bleach into the lungs, which has been associated with developing COPD.
One of my favorites is to continue living and breathing, which is why I'll always go the natural route first, and then move on up the chain as necessary.
I can understand how taking herbs could be called natural, as these grow in nature, but hydrogen peroxide is a harsh chemical made in an industrial process.
Whenever I post any treatments on this forum, be they drug or supplement, I am usually careful to point out possible risks or side effects, because I feel this is important, and I feel it would be irresponsible not to make people aware of the downsides as well as the benefits.