Keratin is a type of protein that’s found in epithelial cells on the surface of the skin. Different types of keratin are responsible for the growth and structure of the fingernails, hair, and skin. Keratin is an intermediate filament-forming protein that provides support and a barrier of protection.
The health of the fingernails, hair, and skin relies on the amount of keratin present in the body at any given time. In the animal kingdom, keratin is found in hooves, wool, and feathers, and it can be extracted and used for supplements, treatments, and other products to help with hair, skin, and nail health.
Hair and many hair products contain keratin
Types of Keratin
There are 54 types of keratin genetically encoded by the human genome and produced by the body. Half of the 54 types are found in hair follicles throughout the body.
Type I keratins are categorised as being the smaller and more acidic type of keratin. They are separated into two groups that work together functionally towards the common goal of epithelial cell health.
Type II keratins are larger than their type I counterparts and have a neutral pH, which can help balance out the pairings of both types when they are synthesising proteins and regulating cell activity.
Alpha-keratins are the exclusive form of keratin found in humans and the wool of other mammals. The structure of the alpha-keratin is fibrous and helical, and both types I and II keratins can fall under the category of alpha.
Beta-keratins are categorised as polypeptide chains and are only found in birds and reptiles, although those species can also possess alpha-keratins. They have been a large contributor to the overall evolution of birds throughout history.
Both alpha and beta keratins help these animals maintain the composition of their claws, scales, beaks, skin, and feathers.
Structure and Function
The structure and function of keratin proteins are determined by their amino acid chains.
These chains are very similar in species across the board. Humans share similar amino acid sequences with bovine species and rats.
Keratin cannot be dissolved in water, solvents, acids, or alkalines, so its structure remains largely intact when exposed to many of the body’s chemicals. Keratin proteins rely on hydration (water) to maintain their overall size and function. 1 To put this into perspective, wool is high in keratin. When a wool sweater is washed in heated water, it shrinks. This is because the keratin proteins lose their length when some of the molecular bonds break at high temperatures.
Hyperkeratosis (excess keratin) can lead to a variety of different conditions.
Hyperkeratosis can develop due to inflammation. Excess keratin is produced as a protective response to skin damage in pressure-related hyperkeratosis, whereas non-pressure-related keratosis occurs for no apparent reason and can be caused by genetics.
Conditions involving keratin include:
Keratosis pilaris (chicken skin)
Although keratosis pilaris can have an unwanted appearance, it is not dangerous in any way.
It happens when keratin clogs pores and blocks hair follicles.
This skin condition causes lesions on the body that can feel like rough sandpaper. The lesions are thought to be a precursor to skin cancer, and your doctor may monitor your skin and/or treat them.
Epidermolytic hyperkeratosis: This form of hyperkeratosis is inherited, and it is present in infants at birth.
This is a type of inflammatory disorder that most commonly affects the flexor (inner) surfaces of the arms and legs. It can be caused by an overproduction of keratin in the body.