If you remember your high school chemistry class, water consists of two hydrogen molecules and one oxygen molecule. Hydrogen peroxide has two hydrogen and two oxygen molecules, and it’s an unstable chemical. When you ingest hydrogen peroxide, it breaks up into water and oxygen. That might sound good, but the bubbles that form will swell in your stomach in the same way that bubbles form when you pour it into your ear or on a wound. Your stomach might not be able to handle this. You’ll wind up vomiting these bubbles, according to the National Capital Poison Center.
If your stomach doesn’t get rid of the bubbles, these bubbles could form an embolism in your blood vessels. An embolism could block blood from flowing to places like your brain, which could cause a stroke. Even though some have claimed that drinking hydrogen peroxide can cure cancer, hydrogen peroxide is actually a carcinogen. A 2011 article in Cell Cycle found that hydrogen peroxide can cause DNA damage, inflammation, and accelerated aging.