The causes of split nails, or onychoschizia, include acute dryness, vitamin deficiency and chemical exposure. Cleaning chemicals or overuse of nail polish remover can cause the nails to become brittle. There are ways to protect the nails from splitting.
People can avoid nail splitting by wearing gloves when using chemicals, applying lotions containing alpha hydroxy acids or lanolin or consuming vitamin B supplements. Gently filing the nails regularly keeps snags and tears of the nail from forming deep splits. Individuals should file the nails into a smooth and rounded shape. Hormones in pregnant women help keep nails strong, and they don't require as much nail care.