Many disorders can affect the nails, including deformities, dystrophies, infections, and ingrown toenails. Infections can involve any part of the nail and may or may not change the nail's appearance. Most nail infections are fungal (onychomycosis—see Onychomycosis), but bacterial and viral infections occur.
The nail unit is made up of the nail plate (the hard part of the nail made of the protein keratin) and the surrounding structures. The nail bed is underneath the nail and attaches the nail to the finger. The nail matrix is located at the base of the nail and is where nail growth originates. The cuticle connects the top of the nail plate to the skin behind it. The lunula is the half-moon shape at the base of the nail. The nail folds are the folds of hard skin at the sides of the nail plate where the nail and the skin meet.
Some of the causes of nail disorders include the following:
Last full review/revision August 2014 by Wingfield E. Rehmus, MD, MPH