In some cases, the cell it hits, becomes modified, and starts to become a cancer cell, reproducing itself, and growing within the body. There's no pain involved, so chances are, the person doesn't have a clue that it's happening. An anti-oxidant is a food nutrient that tends to prevent oxidation within the blood. Anti-oxidants come in a variety of shapes and sizes, and all work to suppress free radicals by preventing oxidation in the blood. Some also do other things, and there is some synergism as well.
Synergism is very important in nutrition.
There are several vitamins that are anti-oxidants. Vitamins A, C, and E are the most common. Vitamin A is also good for vision, and a deficiency causes night blindness. If you don't see well at night, start taking 25,000 IU a day. Vitamin C is well known, but did you know that it is also a viricide, AND a bactericide for the blood.