We ask the experts to settle common questions we've all wondered about.
QUESTION Are white spots on fingernails and toenails an indication of some type of mineral deficiency? If not, what causes the discoloration?
ANSWER White spots on the nails, or punctuate leukonychia (a much scarier-sounding medical name), catch people's attention and everyone likes guessing what they mean. Contrary to popular belief, this phenomenon is not caused by calcium deficiency. Although the spots can sometimes signify a deficiency of zinc, there are many more common explanations.
Often, these mysterious white spots are caused by some sort of trauma to the nail. If severe enough, banging the nail can cause the nail bed to bleed and may result in nail loss. It is the much milder incidents of trauma, such as getting your finger pinched in a drawer, that will cause white spots.
Nails also can turn white because of changes under the nail, in the nail or on top of the nail. For example, if the nail lifts at the end of the finger tip, air under the nail will give it a white appearance.
Nail damage, infection or a disease such as psoriasis can change the nail plate (the actual fingernail, made of translucent keratin) and make it turn white. Changes to the surface of the nail, such as abnormal bits that fall off as the nail grows, will also make it white. A nail is like ice on a lake - if it is damaged, has air in it or under it, or has foreign material in it, the ice will become white rather than clear.
Another unfortunately common cause of trauma is the application of acrylic nails. The process of preparing the natural nails for artificial ones can damage the cuticle. People may also experience allergic reactions, either to the attached artificial nail or to the adhesives used to secure it. In these cases, people may notice white spots when the artificial nail is removed.
In cases where trauma has occurred, the white spots may not show up immediately. The fingernail takes three months to grow out, so it can take four to six weeks before the resulting spots become visible after a minor bang on the finger nail. Because the trauma that causes white spots is often mild, people have a tendency to forget about it by the time the spots appear. These spots should grow out with the nail.
Nail changes can also be a sign that something else is happening in the body. White spots can be seen in combination with a type of hair loss called alopecia areata, an autoimmune disorder. The hair condition appears as bald circles on the head and may go unnoticed for a while. It is often a barber or hairstylist who discovers this hair loss first.
Dr. Neil Shear is head of dermatology at Sunnybrook Health Sciences Centre and professor and chief of dermatology at the University of Toronto.