It sounds like brittle nail syndrome, which occurs when the nail plate is unable to maintain moisture and becomes dehydrated. It occurs most frequently in individuals who already have a tendency for dry skin. This is because the syndrome is like having “dry skin of the nails.” There are many causes for this syndrome. In an otherwise healthy individual this can be treated by applying moisturizers to the nails on a regular basis and by taking oral biotin supplements, a minor B vitamin, daily. In addition, people with this disorder should avoid nail products containing formaldehyde or acetone.
Occasionally, the syndrome can be caused by medical problems. These include an underactive thyroid, low iron or zinc levels in the blood, or, if a sudden onset of this condition occurs in an elderly person, it might indicate a systematic disorder. All of these cases require a doctor’s evaluation.
Excess use of soap and water with strong chemicals or detergents can also be the cause of brittleness. If so, minimize exposure by wearing gloves and by not immersing hands for long periods.
If there are only ridges in the nails going from the cuticle outward, then this may simply be due to the aging process. There is no way to prevent ridges associated with aging, but lightly buffing the nails no mire than once every 10 days should eliminate them. -- Dr. Scher