Hydrogen peroxide can be found in the pharmacy section of most drugstores in a dark brown opaque bottle. The reason that it is kept in an opaque brown bottle is that light will actually cause the hydrogen peroxide to break down and weaken its potency. In any case, just look for a brown bottle with a white cap, which is the ubiquitous way of storing hydrogen peroxide around the country. While this should not be a problem if you just buy your hydrogen peroxide from the local drugstore like Walgreens or Longs Drugs, it is important to get a 3% hydrogen peroxide solution, which is the maximum potency that is generally accepted to be safe for biological and health purposes. Any hydrogen peroxide sold in a drugstore should be 3%, but double check to make sure that you have not inadvertently purchased a bottle of hydrogen peroxide for industrial use instead of household use.
Hydrogen peroxide is useful as a mouthwash due to its antiseptic properties, the same properties that render hydrogen peroxide effective in preventing infection in cuts and scrapes. Hydrogen peroxide is also an effective whitening agent, and you will notice that almost every home teeth whitening kit has hydrogen peroxide listed as one of its active ingredients. Most of those home teeth whitening kits are ridiculously expensive however, since most oral hygiene manufacturers are trying to cash in on the fad. It is very easy to accomplish the nearly the same result yourself, however, with a much more affordable bottle of hydrogen peroxide from the drugstore.
I have found that I prefer hydrogen peroxide as a pre-brushing oral rinse. To begin the process, it is best to rinse your mouth out with ordinary water first to rinse your mouth of any debris. After this is accomplished, measure out a small amount (a couple of tablespoons should do it) of hydrogen peroxide into a cup and rinse your mouth with the peroxide for thirty to sixty seconds. If you like, you can just take a small swig from the bottle, which is what I usually do myself. Almost immediately the hydrogen peroxide will start to bubble and foam, which is a result of the chemical reaction between the hydrogen peroxide and the contaminants in your mouth. It is important not to use too much hydrogen peroxide at one time since its volume will expand in your mouth due to the foaming action. The foaming action will penetrate to all areas of your mouth, even between your teeth and will help to rid your mouth of harmful bacteria that can cause bad breath or gum disease. The hydrogen peroxide instructions on the bottle suggest diluting the hydrogen peroxide with equal parts water before using as an oral rinse, but nearly every dentist I have consulted on this issue has stated that dilution is unnecessary. After rinsing your mouth with the hydrogen peroxide, then flush your mouth again with water and brush your teeth like normal. You will find that your teeth feel cleaner and are noticeably whiter after this process is repeated for several days.
In conclusion, the whitening and antiseptic properties of hydrogen peroxide make hydrogen peroxide an excellent mouthwash for overall oral health. It may take several applications of peroxide for the whitening to be noticeable, but afterwards your teeth will be significantly whiter at a fraction of the cost of purchasing a home teeth whitening kit.