To the extent that nails provide clues to health, these clues are usually too little, too late.
Years ago, when sophisticated diagnostic tests were not available, doctors sometimes looked to the appearance of nails for clues to a patient’s health, said Dr. Howard Baden , a dermatologist at Massachusetts General Hospital. “And the nails do change with some diseases. But by the time the nails are involved, the patient is pretty sick,” he said.
Although not good for diagnostic purposes, fluctuations in health can show up as changes in nails. Many people, for instance, have longitudinal lines on the nails. But these occur with normal aging and “don’t mean anything is wrong systemically,” said Dr. Rebecca Kazin , associate professor of dermatology at Johns Hopkins University.
On the other hand, ridges that cross the nail often occur with acute illness or other severe bodily stress such as chemotherapy. The nail stops growing, then starts again, creating grooves that grow out when the person recovers.
“Club nails,” which become very convex, or domed, can be a sign of chronic low blood-oxygen levels, which can occur with chronic lung or heart disease. Spoon nails, which often run in families, don’t mean anything medically, although doctors used to think they were a sign of iron deficiency.
Nails can also change color with certain diseases. So-called yellow nail syndrome is sometimes associated with cancer, immunodeficiency syndromes, and some other conditions.
Very pale nails, sometimes called half-and-half nails, may be associated with liver or kidney disease. Pitted nails can be a sign of psoriasis.
The only warning signal that you might pick up early by looking at your nails is melanonychia, a longitudinal line of brown. If this doesn’t grow out, it could be a sign of skin cancer in the nail matrix, from which the nail grows.