What Is Hair and How Does It Grow?

Hair is a protein called keratin, which is a fibrous and helix-shaped substance that forms most of the body’s phanera (hair, nails and claws). It is 95% water, with the remainder consisting of a variety of amino acids, minerals and vitamins. Hair color comes from two pigments, eumelanin and pheomelanin. These are deposited into the hair pigment cells, which then gives the hair its color and also helps protect the hair cell from damaging UV rays. As we age, our hair follicles slow down production of melanin and the color starts to fade, leading to gray or white hair.

A hair follicle grows from the skin’s surface and is located within the dermis layer of the scalp. It is surrounded by a sebaceous gland, which produces lipids called sebum. This lubricates the hair and provides nourishment. Blood vessels run deep into the follicle and deliver nutrients to the hair cell. As these cells grow, they push out older cells and the resulting string-like structure we see as our hair is born.

The shape of the hair follicle determines the texture and style of your hair. Circular follicles produce straight hair while oval follicles make curly or wavy strands. Each strand of hair is made up of hundreds of smaller strands of keratin.

Each hair has an outer sheath and inner core, with a medulla in the middle. The cuticle is a hard, protective outer layer of scale-like cells that encloses the more delicate parts of the hair. The core is the part that contains the most nutrient-rich material and is a key part of its strength and resilience.

Hair has been in the human family for 300 million years. It is thought that it came from a common ancestor with mammals, the synapsids. It is not known exactly when the synapsids acquired hair or other mammalian characteristics, as fossils are rare.

Generally, most people have between 100,000 to 150,000 hairs in their scalp and lose up to 100 each day. They are grouped into follicular units, groups of 1 to 4 follicles that produce thick terminal hair. Currently, 90% of your hairs are growing in a phase of active growth called anagen, which can last up to 7 years. The remaining 10% are in a resting phase called catagen or telogen, which typically lasts 3 to 4 months. It’s not uncommon for a single hair to be in different phases at the same time, which is why a person might have a few stray strands on their head. A shampoo formulated with ingredients like nourishing cupuacu seed butter and glycerin can help. A hair mask enriched with shea butter, acai and avocado oil can also be helpful for repairing damaged strands. You can find a wide range of hair products at your local drugstore or beauty store. The important thing is to find one that works for you and your hair’s needs. For example, if your hair is curly and prone to frizz, you might want to choose a product containing glycerin and acai oil, or one that hydrates with shea butter and ginseng.