Ah, yes, the antioxidant. While nearly everyone has heard of them, few know how they actually work. But it’s relatively simple.

Let’s get into some basic chemistry. Oxygen molecules are stable, or unreactive, when they have an even number of electrons. However, when oxygen molecules combine with other molecules, the oxygen can end up with an odd number of electrons. The oxygen molecule is now unstable and highly reactive, and the odd-numbered species is known as a free radical. This free radical really is a crazy, radical species: it starts a vicious chain reaction that attacks cells, proteins, and DNA, all of which contribute to aging.

The body defends against free radicals with antioxidants, which impede or slow the chain reaction. Antioxidants like beta carotene and vitamins C and E “break the chain,” stopping free radicals from ripping electrons off of other molecules. Other antioxidants, like superoxide dismutase, catalase and glutathione peroxidase, stabilize the unstable, reactive free radicals, and thereby slow the free radical chain reaction.

Unfortunately, the body does not produce or ingest enough antioxidants to neutralize all of the free radicals, which come from processes that are both endogenous (within the body, such as human metabolism) and exogenous (outside the body, from pollution, smoking, alcohol, and UV radiation, amongst other sources). Over time, this means free radicals accumulate a great deal of damage within the body (WebMD). As a means of defense against future UV-induced free-radical damage, most dermatologists recommend daily use of sunscreen with UVA/UVB protection and a SPF of at least 15. However, according to Skinceuticals, sunscreens only block 45-55% of free radical production. As such, many experts recommend a second line of defense, by using antioxidant supplements and antioxidant-rich topically applied treatments.

However, beware of overloading on antioxidant supplements. Although studies repeatedly conclude that levels of antioxidant vitamins found in most popular multivitamins are safe, it is easy to increase intake to toxic levels. Some of these levels are provided in this article from the Harvard School of Public Health, and additionally from How Stuff Works below:

In addition to antioxidant supplements, take care selecting a quality antioxidant skincare product. According to Cosmetic Dermatology, vitamins C and E, glutathione, lipoic acid, and coenzyme Q10 are “network antioxidants,” which work together synergistically to regenerate or enhance their action. For instance, after vitamin E is used to neutralize a free radical, vitamin C or coenzyme Q10 can donate electrons to vitamin E, effectively “recycling” it in the system. For this reason, antioxidant products like Skinceuticals C E Ferulic are particularly valuable; when used with a sunscreen, this product has been shown to provide eight times the free radical protection of sunscreen alone.

Although antioxidants provide ample protection against future free radical damage, antioxidants have not as of yet been shown to reverse existing signs of aging. According to Paula Begoun, bestselling author of Don’t Go to the Skincare Counter Without Me, it is further unknown how many antioxidants are necessary to stop all or even most free-radical damage, or for how long antioxidants are effective before being used up. However, based on current research, antioxidants provide excellent prevention against aging, and should be used as a part of your regular skincare regular regimé.