Free radicals (reactive oxygen species) — electrically charged, highly unstable, and very reactive oxygen atoms or molecules. Free radicals are formed when an oxygen atom loses an electron. To regain stability, free radicals capture electrons from other substances in order to neutralize. This reaction can give rise to two different processes: (a) the neutralization effect of one free radical can cause the formation of another, causing a chain reaction of free radical formation where innumerable free radical reactions occur within seconds of the initial reaction; or (b) it can attach itself to the cellular membrane, damaging the DNA and cellular repair mechanisms, etc. This is why it is important that the skin has a reservoir of anti-oxidants. Externally, free radicals are a result of UV radiation, pesticides, air pollution, drugs, cigarette smoke, stress, and unhealthy lifestyles. The body has its own natural mechanism of protection against free radical-induced damage. This protective ability diminishes with age and when the body is exposed to situations where the quantity of free radicals formed is greater than the body’s natural ability to neutralize them. Free radicals are considered the number one factor behind skin aging. They damage DNA, cellular membranes, and the dermal connective tissue, particularly collagen, by stimulating collagenase enzyme production. The overall result is cellular damage, alterations in the structure of the cellular membrane, and decreased skin elasticity and pliability. Free radicals also harm the Langerhans cells, diminishing the efficacy of the skin’s immune system.