In the case of iron rust, oxygen atoms eat away at the metal. In the case of "biorust" free radicals eat away at human tissues, at human cells. Not infrequently, free radicals do contain oxygen, a particular form of oxygen that is in a very active state. They attack tissues and cells by forming bonds with atoms that are part of the cell, tearing them away from their cellular structures, and sometimes setting other charged atoms adrift as well - in essence creating more free radicals. In that case the damage is twofold.

Free radicals may attack various body tissues, including collagen and elastin, which are integral components of the skin. These components keep the skin moist and elastic. It is the action of free radicals within the cell that generates some of the aforementioned lipofuscins, ultimately producing age spots. With the passage of time, as the damage (biorust) from the free radicals becomes pronounced, normal skin comes to take on the feel and appearance of scraped parchment.

Besides attacking the tissues and cells of the skin, free radicals can attack other parts of the body, such as heart and kidney tissue. Further, their activity can interfere with the inner chemistry of the cell, disrupting the DNA and RNA, as well as the synthesis of proteins.

Because the action of these free radicals is chemically that of an oxidant, those substances that have shown themselves to be effective in combating them are referred to as anti-oxidants.