Hair plays an important role – not only for a person’s aesthetic appearance but also for protecting the skin from external influences. However, few people think about how hair actually grows and what lies behind this seemingly simple process. A central element in this mechanism is the hair follicle – a complex skin structure from which each individual hair emerges.
Hair follicles are not only responsible for hair growth, but they also regulate body temperature and respond very sensitively to hormonal and external changes. In this article, we will take a closer look at the structure, functions, and importance of hair follicles and explain which factors can influence their functioning.
Hair follicles are located deep within the skin – this is where the growth of each hair begins. They are small but highly complex structures in which the hair is formed and further developed. The follicle represents a small depression in the skin that contains the hair root. The visible part of the hair that protrudes from the skin is called the hair shaft.
The first follicles begin to form as early as the fifth to sixth month of embryonic development. An adult human can have up to five million hair follicles, with each follicle capable of producing very different hair types – from fine and soft to thick and strong hair. These structures are also equipped with sebaceous glands, blood vessels, and nerve endings, making them essential not only for hair growth but also for the overall protective function of the skin barrier.
What parts make up a hair follicle and how do they function?
Hair Funnel (Infundibulum)
The visible hair shaft is a direct continuation of the hair root and grows from the so-called hair funnel – a small indentation in the skin. Below this funnel, the shaft transitions into the actual hair follicle, which consists of the hair root and the surrounding tissues.
Hair Sac (Follicular Saccule)
The word "follicle" comes from Latin and means "small bag" or "sac". It refers to a specific indentation in the skin where the hair root lies. This sac is also called the root sheath. The hair follicle expands downward to form the so-called hair bulb (bulbus). During laser hair removal, the light beam specifically targets the stem cells in the hair bulb, destroying them and thus preventing further hair growth.
Other Structures of the Hair Follicle
Attached to the follicular sac are sebaceous and sweat glands. Directly below is the arrector pili muscle, which makes the hair stand up in response to cold or emotional reactions such as stress or fear ("goosebumps").
At the lower end of the hair follicle is the hair papilla. It consists of a network of capillaries, connective tissue, and nerve endings and serves a nourishing function: the papilla supplies the hair cells with all the necessary nutrients for hair growth.
The Chemical Composition of Hair
Chemically speaking, hair consists of about 95% keratin – a fibrous protein that provides strength and elasticity. Around 2% consists of lipids (fats), about 1% of pigments, and a small portion of minerals. All these components are connected by various chemical bonds that determine the shape and stability of the hair. This knowledge is specifically applied in trichology for hair treatment and care.
Pigmentation of Hair
Melanin is the main pigment that determines hair color. This biologically active molecule is produced by specialized cells called melanocytes, which are located in the hair follicles (hair roots). There are two main types of melanin: eumelanin and pheomelanin.
Eumelanin gives the hair dark tones such as:- Black,
- Dark brown,
- Chestnut brown.
The hair color produced by eumelanin depends on the amount and concentration of this pigment in the hair. The higher the eumelanin content, the darker the hair.
Pheomelanin is also produced in the hair follicles but gives rise to light tones such as:- Red,
- Orange,
- Golden blonde.
This pigment is present in lower concentrations than eumelanin.
Interesting: The number of hair follicles is related to natural hair color. People with red hair typically have a lower hair density – about 60,000 to 80,000 hair follicles. In blond individuals, the number of follicles can be up to 150,000.
Genetics plays a crucial role in determining the hair color of each individual. It influences not only the amount but also the type of pigment produced – resulting in the individual color palette of our hair. Depending on ethnic origin, different hair colors are typical: People of European descent usually have lighter tones such as blonde or light brown, but also dark shades are possible. In people of Asian or African descent, very dark hair – from black to dark brown – predominates, although light exceptions also exist.
Factors Influencing Hair Growth and Health
Genetics and Age
Genetics plays a key role in the individual characteristics of hair and hair follicles. It determines, among other things, how sensitive the hair follicles are to dihydrotestosterone (DHT) – a hormone that can accelerate hair growth but also promote the development of androgenetic alopecia (hereditary hair loss). The stronger the genetic sensitivity to DHT, the higher the risk of hair loss, especially with increasing age.
Hormonal Balance and Hair Growth
Hormonal balance significantly influences the growth and activity of hair follicles. Hormonal disorders – such as those occurring with polycystic ovary syndrome (PCOS), thyroid diseases, or during pregnancy and menopause – can inhibit hair growth or lead to excessive hair loss.
Hair Care and Damage to Hair Follicles
Improper hair care – such as very tightly tied hairstyles or frequent use of heat-styling tools – can damage hair follicles and lead to so-called traction alopecia. Choosing gentle care and styling methods helps to keep hair follicles healthy and reduce the risk of hair loss.
Stress and Hair Health
Chronic stress negatively affects the health of hair follicles and can lead to thinning hair or increased hair loss. Mindful stress management and promoting general well-being help to maintain healthy hair and hair follicles in the long term.
Environmental Influences on Hair Follicles
Environmental pollution, intense sun exposure, and extreme weather conditions can negatively affect the health of hair and hair follicles. Protecting the hair from harmful environmental factors and regularly using high-quality hair care products is essential to maintain healthy follicles and promote hair growth.
Sleep and Hair Health
Adequate sleep is important not only for general well-being but also for healthy hair follicles. Good sleep hygiene supports the regeneration of the scalp and hair follicles – contributing to strong, healthy hair.
The Effect of Smoking on Hair Follicles
Smoking impairs the blood circulation of the scalp and thus the supply of hair follicles with essential nutrients and oxygen. This can slow hair growth or promote hair loss. Quitting smoking improves blood flow and can support the growth of healthy hair.
Inflamed Hair Follicles (Folliculitis)
Folliculitis refers to the inflammation of hair follicles. It can occur on any hairy part of the body. The scalp is particularly often affected – here, inflammation usually appears as irritation, redness, itching, or small pustules. The cause is often bacterial or, more rarely, fungal infections. Mild cases of folliculitis can be treated at home. In more severe cases – such as those involving scarring, severe pain at the follicles, or persistent itching – medical evaluation is important. Without treatment, acute hair loss may occur.