Keratin is a very strong protein that our hair, nails, skin and teeth are made out of. The amino acids with their unique properties are combined together to form keratin which can be hard and inflexible (like hooves) or soft like your skin. This depends on the levels of the various amino acids. Most of the keratin that we deal with everyday is actually dead. Our hair, skin, and nails are formed from dead keratin cells our body sheds regularly as new cells push up from underneath. If we are trying to keep these dead keratin cells in good condition, they will work as an insulating protecting layer for the delicate new keratin below them.
Keratin is almost non-dissolving due to cysteine disulfide it contains, which means Keratin can create disulfide bridges. These bridges form an extremely strong helix shape. Across the helix sulfur atoms bond to each other, creating a fibrous matrix that is not readily soluble. Depending on the concentration of cysteine disulfide in keratin, the bond can be very strong to make extremely hard cells like hooves, or it can be much softer to form flexible keratin like your hair and skin. These high levels of sulfur in keratin give a distinct sulfurous odor when Keratin is burned.
Keratin is formed by keratinocytes. Keratinocytes are living cells that make up a large part of your hair, skin, nails, and other parts of the body. These cells slowly push their way upwards, they die and form a protective layer of cells. Several thousands of them are shed every day, and this process may be accelerated by various medical conditions like psoriasis. If the external keratin layer got damaged it may result in unhealthy of flaky look of skin, hair, and nails.
A lot of people complain about their hair and nails being dry and brittle. This happens because the dead keratin is being pushed to great lengths; but there’s a way to grow out your hair and nails and keep them healthy at the same time – eat food like gelatin and moisturize the hair and nails on regular basis.
Generally speaking, the thicker the layer of keratin, the healthier the hair or nails are; outside dead cells protect the living cells at the core. By moisturizing the external layer of keratin you will keep it healthy and also prevent it from cracking and splitting, whether the keratin is forming your nails, hair or skin.