A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

What causes white spots on your fingernails?

December 7, 1990

Dear Cecil:

Please end the anxiety I've suffered over this question. What are those white spots that appear on my fingernails and where do they come from?

Cecil replies:

Sorry to lay this on you, kid, but I figure if you're going to be anxious, you might as well be anxious big time. What you've got is what's known as punctate leukonychia (medicalese for "white spots.") Extreme cases of leukonychia, in which the nails turn entirely white (leukonychia totalis) or develop white bands (striate leukonychia), can indicate anything from arsenic poisoning to leprosy. Leukonychia has also been linked to typhoid fever, frostbite, trichinosis, gout, diphtheria, cholera, acute rheumatism, myocardial infarction, colitis, and any number of other ghastly ailments.

But don't sweat, you probably don't have any of them. Mere spots are extremely common and undoubtedly harmless. The folklore about them goes back for centuries; they've been called "gift spots," "fortune spots," and for some reason "sweethearts." As with many other minor medical curiosities, little research has been done on punctate leukonychia in recent years. The white color has been variously attributed to trapped air and to defective keratinization, keratinization being the process by which nails are formed. The air bubbles and/or opaque, imperfectly keratinized granules within the nail cells refract light and the spot appears white.

The precise cause of leukonychia is a mystery. It's said to be more common in the young and in women, and often shows up when the body undergoes stress or trauma, such as a blow to the fingertips. Excessive manicuring can make things worse; so can working in a pickle factory, of all things. So pitch the nail file (a bit too '40s anyway, don't you think?), quit packing those kosher dills, and I'm sure those damn spots will be out in no time.

Zinc spots

Dear Cecil:

I enjoy your column but this time I'm afraid you've missed. White spots on the fingernails are often a sign of zinc deficiency. One source of documentation is Dr. Pfeiffer's Total Nutrition by Carl C. Pfeiffer, Ph.D., M.D., former director of the Princeton Brain Bio Center (now deceased). He writes, "Remember that one of the easily recognized signs of a zinc deficiency is the appearance of white spots on the fingernails."

The late Carleton Fredericks talked of this many years ago also. I had white spots for a long time, as did one of my sons. Fifty milligrams of zinc daily stopped the spots. Doctor Fredericks said some individuals either have a greater need for zinc than most people or else a lessened ability to utilize available zinc in the average diet.

Cecil replies:

I'll amend my remarks to this extent: an abundance of large white spots or bands may be a sign of zinc deficiency. But it would be wrong to suggest that zinc deficiency is always, or even usually, the cause of spotting. As I said in my column, there's a long list of things that can cause leukonychia, or nail whitening. If you think zinc deficiency is a bummer, try malaria, Hodgkin's disease, or sickle cell anemia. However, "in the great majority of punctate [spotting] cases …, which are extremely common, no cause can be found" (The Nails in Disease, Samman and Fenton, 1986).

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