Occurrence that takes place at an atomic level and is a complex physiological process. Molecules are comprised of atoms. Atoms comprise all matter. Atoms are made up of protons, neutrons, and electrons. Electrons occur in pairs, and when an element only has a few paired electrons it can easily become unstable.
Oxygen and oxides are primary examples of potential unstable elements in our environment. When oxygen interacts with skin (and because the air we breathe is 20% oxygen, that happens all the time), it almost always loses one of its electrons. This oxygen molecule, which now is minus one electron, is a damaging environmental factor.
Because it is now unstable, the oxygen molecule quickly finds another electron, and it does this by taking an electron from another molecule in the skin, which is usually a healthy substance such as antioxidants in the skin. Antioxidants have lots of electrons to spare. Once those substances are robbed of all their electrons they break down and are destroyed. Oxygen molecules (or other potentially damaging environmental factors) attempting to replenish themselves in this way trigger a cascading event. The reactions that cause environmental damage take place in mere fractions of a second. Antioxidants are substances that prevent oxidative damage from beginning.
The primary causes of environmental damage on skin are pollution, air, cigarette smoke, herbicides, and solvents (such as alcohol). Antioxidants are a way to potentially neutralize these effects via topical application.