Brittle nails are caused by excessive submersion of the nails in water, or periods of ill health, or nails dried out from indoor heat, exposure to detergents and too frequent use of nail polish removers. To prevent brittle nails you could avoid exposure to detergents, cleansers and other strong cleaning fluids - or wear gloves; protect your nails from little bumps and possible injury by wearing cotton gloves; and keep your nails short because the shorter the nails the less the risk of damaging them.