I'm laid up on the sofa today with vertigo from an ear ache, so in the name of science I turned to pinterest to research home remedies (of course, by "science" I actually mean ridiculous home remedies I can test and research).
So, does putting a simple solution of hydrogen peroxide in your ear let you know if you have an infection, as well as treat said infection? NOPE.
You see, hydrogen peroxide is just simply water with an extra oxygen molecule to it - H202. Now that's not to say it's the same as water, simply altering or adding various single molecules to things can change them drastically. But that's not the case with things like hydrogen peroxide.
But why does it bubble when you add it to a cut? Because of a simple thing called catalase. Pretty much everything from fruits and veggies to human tissue contains this enzyme. When exposed to the peroxide, it causes the H202 to break up, and allows the extra oxygen molecule to free itself, causing the bubbles. Ta-DA! Even if you're ears are clean and free of infection, chances are good the peroxide will still bubble and foam, so that's really not a good way to test for an infection. Want to test this out? Pour a small amount in a glass and use it as a mouthwash, and enjoy as your mouth fills with bubbles! Just be careful not to choke or gag!
But how about the second claim? Will it at least treat an infection if you have one? Maybe, but it's not likely. Results are mixed as to if this works or not. It's important to realize that there are various causes for ear infections, from viruses like those that cause colds, to allergies, not to mention bacterial infections which require antibiotics (peroxide is NOT recommended for killing bacteria, as it doesn't kill everything and can actually cause scar tissue to form, something you don't want in your ears). What it is quite good for though, is helping with ear wax removal - in fact ear wax drops are typically nothing more than mineral oil and peroxide. So all-in-all, you can put peroxide in your ears, but it's not going to let you know if you have an infection, and it's most likely not going to cure anything. It's not uncommon for a lot of earaches to only last a few days on their own, so if you find relief using this trick (or warmed oil, which is also a common ear ache treatment) then go for it. However if your ears aren't better after a few days then it's time to seek professional help.