My 4yr old child faints each time he gets hurt. Is this unusual?

He could be having. Breath-holding spells, which can be treated by having him breathe into a paper bag. Or a vagal reaction like some people have at the sight of blood. Video an episide to show his pediatrician.
Very. This strongly suggests that he has biochemically induced limbic system dysfunction and i would guess that he has other symptoms, particularly in behavior, temper tantrums etc. The easiest way to do this is "junk" ingestion, for it is widespread in the U.S.