A person's fingernails can flake as he ages, since the nails become weaker with time. Damage to the nails, such as through excessive dishwashing or swimming, can also cause flaking.
A dietary deficiency can also lead to flaking nails. A lack of calcium in the diet, as well as deficiencies in vitamins A, B12 and D, can weaken the nails and cause them to flake. Individuals with certain medical conditions can also experience nail flaking. A disorder of the kidneys, thyroid or liver can weaken the nails and cause flaking and cracking. Psoriasis or nail fungus can also make the nails flake.