35% Hydrogen Peroxide
Most people are familiar with diluted (3%) concentrations of hydrogen peroxide used for wound cleansing. However, hydrogen peroxide is available in many concentrations, including industrial strengths (10% or higher) that are popular in some branches of alternative medicine. These industrial strengths are not intended for human consumption.
Although the so-called "food grade" hydrogen peroxide (35%) sounds like it is safe to consume, the term "food grade" in this case simply means that the product is appropriate for use in the preparation or storage of certain foods, such as tripe, dried eggs, or herring.
According to the U.S. Food and Drug Administration (FDA), people should not purchase or use high-strength hydrogen peroxide products (including 35% hydrogen peroxide) for medicinal use because they may cause serious harm or death.
The FDA further warns that high-strength hydrogen peroxide is not approved by the FDA for any purpose and that "no one has presented any evidence that hydrogen peroxide taken internally has any medical value."
(To learn more, click Food Grade Hydrogen Peroxide. This article sheds more light on why the higher strengths of hydrogen peroxide such as 35% can be so dangerous and lists precautions to take if you decide to disregard the FDA's warnings.)