Healthy Fingernails

"Just like the eyes are the window to the soul, so are the nails," says Tamara Lior, MD, a dermatologist with Cleveland Clinic Florida. Lior says she once convinced a patient to have his lungs checked after noticing a bluish tint to his nails, a sign that he wasn't getting enough oxygen. Sure enough, he had fluid in his lungs.

Warning signs for many other conditions, from hepatitis to heart disease, may also appear when previously healthy fingernails undergo changes, according to Joshua Fox, MD, director of Advanced Dermatology and spokesman for the American Academy of Dermatology. "Changes in the nails can be a sign of a local disease like a fungus infection or a sign of a systemic disease like lupus or anemia," Fox tells WebMD.