Horizontal grooves, called Beau’s lines, can appear when nail growth temporarily slows after a severe illness, fever, surgery, major stress, or certain medical treatments. Brittle or spoon-shaped nails may also be associated with iron deficiency or thyroid problems.
Changes in nail color can provide other clues. Persistent yellow, blue, very white, or dark-streaked nails may sometimes be related to infections, circulation problems, lung or heart conditions, liver disease, diabetes, or, rarely, skin cancer.
Because nails alone cannot diagnose a disease, persistent or rapidly changing marks should be examined by a healthcare professional—especially when accompanied by pain, breathing problems, fatigue, swelling, or changes in the surrounding skin.
