Sometimes fingernails may have white spots. These are called leukonychia. These are actually some kind of scar or bruise caused by a prior injury on the nail bed. They are not, as some people think, a symptom of a deficiency in vitamins or minerals.
The reason why people don’t associate white spots on fingernails with injury is that it may take days or sometimes even weeks before the spot becomes noticeable. By the time they realize they see it, the little accident that caused it—hitting a nail on a door, or biting it in a fit of nervousness—has slipped their memory.
White spots are usually caused by very minor injuries. More serious impact, such as what one would get by accidentally slamming a nail on the finger (ouch!) would result in black spots. Very serious injuries could even lead to necrosis, or what most people know as “a dead nail.” Dead nails are usually black and unusually thick.
Most nail injuries are not serious. While there is no “cure” for it the nail will naturally grow, usually at a rate of half an inch every four weeks, so the spots will eventually be trimmed off at the next manicure or pedicure. Usually white spots will fade even before they grow out.
White spots can also be caused by an allergic reaction to nail care products such as polish, polish remover or hardener. Yellowish spots, on the other hand, are sometimes signs of fungal infections. It is best to stop using nail care products until the white spots disappear, and the nail returns to its natural healthy color.