Just like the skin, nails are a barometer of general health. Marks and colour changes can be a sign of malnourishment or diseases -- past, present and future. Most ridges and white lines are a signal of nothing more sinister than slight nail damage, but occasionally, they indicate something that should be checked out by a medical professional.
White nail, or leukonychia, is caused by the presence on the nail bed of parakeratotic cells which do not reflect light. These make the nail or portions of it appear white. White stripes on the nails are called "partial leukonychia" and can be either traverse -- across the nail -- or longitudinal. The lines do not necessarily appear on every nail. Partial leukonychia can also be a phase of total leukonychia and appear as a result of having suffered tuberculosis or Hodgkin's disease.
Traverse partial leukonychia frequently appears on the nails of women and is generally caused by matrix trauma during manicure. The cause of white lines on toenails is often attributed to badly fitting shoes. In extremely rare cases, these lines are a sign of arsenic poisoning and are called "Mees' lines." Other conditions that can cause traverse white lines include herpes, measles and malaria. Longitudinal white lines may be associated with Darier's disease.
Longitudinal ridges on the nails may be no more than a sign of age, according to Jessie Lowenfelt, of McGill University. The nail bed itself is arranged in parallel lines that run in the direction of growth. As we age, these lines become more prominent. Horizontal ridges, or "Beau's lines," appear after serious physical or emotional illness has hindered nail growth. These ridges will eventually grow out in about six or seven months, which is roughly the time it takes for a completely new nail to grow.
To prevent ridges and white lines on nails, it's important to eat a healthy well-balanced diet, said Lowenfelt. Nails shrink and swell in water, making them brittle. Rubber gloves can help protect nails and moisturisers and cuticle cream will help keep them nourished. Nail polish stops nails from "breathing" and nail polish remover should be used sparingly, as it is very drying. Most importantly, manicures should be gentle.