Vertical, or longitudinal, ridges on the nails are normal and do not indicate a health problem. Ridges that run horizontally along the fingernails usually indicate an overall health issue. These lines may be referred to as Beau's lines, although Mees’ lines and Muehrcke’s lines are also diagnosed.
Beau's lines can indicate something as simple as a zinc deficiency, or something more serious like diabetes, vascular disease, or sickness including a high fever such as scarlet fever and measles, or even Raynaud’s disease.
Mee's lines do not always occur on all nails, and usually indicate arsenic poisoning, although they are also associated with Hodgkin’s disease, malaria, and chemotherapy.
Muehrcke’s lines are white lines that go all across the nail, and it occurs in the nail bed, so it doesn't move as the nail grows. These lines indicate that a person probably has Nephrotic Syndrome.
Vertical ridges on the nail appear more obvious as a person ages, similar to wrinkles on the skin that also increase with age. The ridge is the thinnest part of the nail, and if it is buffed, the nail can split. The better way to treat the ridges is to increase moisture to the nails by applying lotion to the nails, especially to the cuticles.