Keratin is a protein contained in hair, skin and nails. A keratin build-up under the toenails can cause the nail to become brittle and discoloured. The toenail also can separate the nail from the nail bed, but only in extreme cases. White keratin spots might be caused by something as simple as missing nutrients in the diet; however, psoriases and onycholysis might also be causing them.
What Is Keratin?
According to Nail Solutions, keratin is produced by the matrix of the nail. The matrix is the root of the nail and is not visible. It is protected by the proximinal nail fold. The keratin cells make up the cell plate. Normally these keratin cells are pushed forward and made flat, which makes the nail bed look clear. In cases in which there is an extra amount of keratin, white spots form on the nail.
Keratin develops under the nail beds of both toenails and fingernails because of something called onycholysis. According to BBC Health, onycholysis is the separation of the nail from the nail bed. It doesn't hurt because it is a gradual process. A common cause of onycholysis is trauma, but other possibilities are psoriasis or lichen planus, thyroid dysfunction, fungal infections, medication side effects, chemicals like nail polish remover, or prolonged immersion in water.
According to the International Eczema Psoriasis Foundation, when keratin builds under the nail bed the nail appears white in spots. Keratin spots may only appear on one nail, but in some people it may affect more than one nail.