What causes white fingernail spots?

A fellow caregiver asked...

I have white spots on my fingernails and they also have ridges going up and down them. What could be causing these white fingernail spots?

Expert Answer

Jennifer Serafin, N.P. is a registered nurse and geriatric nurse practitioner at the Jewish Homes for the Aged in San Francisco.

White spots on fingernails are usually the result of trauma to the nailbed.  In other words, you hit your finger on something, and then the next day, a white spot will appear on your nail.  The white spot will eventually grow out, but it can take awhile for that to happen.  Nails grow slowly, so it can take weeks for something like this to go away. Rarely, white spots can be caused by a zinc deficiency,  Keep in mind that in order to develop a nail problem from lack of zinc, you would have to be severely deficient, showing other strong signs of zinc deficiency as well, such as patchy hair loss and extremely dry skin.  

As for vertical ridges, these are usually harmless.  They can become more pronounced with aging, although the exact cause for this is not known. 

Horizontal ridges can be caused by diseases like respiratory illness, malnutrition, or trauma to the nailbed.  It is best to get this checked out by a dermatologist, to make sure an underlying health problem is not to blame.