Hair Biology and Growth Cycle

The Structure of Hair

To understand hair growth, it's essential to first understand the basic structure of a hair strand. Hair is primarily composed of a tough, fibrous protein called keratin. Each hair strand consists of three main layers:

• Cuticle: The outermost layer, composed of overlapping, scale-like cells that protect the inner layers. A healthy cuticle lies flat, reflecting light and making hair appear shiny. Damage to the cuticle can lead to roughness and dullness.
• Cortex: The middle and thickest layer, which contains the melanin that determines hair color. The cortex provides hair with its strength, elasticity, and texture.
• Medulla: The innermost layer, present in some but not all hair types. Its exact function is not fully understood, but it may play a role in hair's structural integrity.

The hair strand itself is non-living. The living part of the hair is the hair follicle, which is a pocket-like invagination of the epidermis that extends into the dermis of the scalp.

The Hair Follicle

The hair follicle is a complex mini-organ responsible for hair production. Key components include:

• Dermal Papilla: A cone-shaped structure at the base of the follicle, rich in blood vessels that provide nutrients essential for hair growth. It also contains specialized cells that signal hair growth.
• Hair Matrix: Located above the dermal papilla, this is where rapid cell division occurs, forming the new hair shaft.
• Sebaceous Gland: Attached to the follicle, this gland produces sebum, an oily substance that lubricates the hair and scalp, providing a protective barrier.
• Arrector Pili Muscle: A small muscle attached to the follicle that contracts in response to cold or fear, causing the hair to stand on end (goosebumps).

The Hair Growth Cycle

Hair growth is a continuous, cyclical process. Each hair follicle operates independently, meaning hairs are constantly in different stages of the cycle, preventing all hair from shedding simultaneously. There are three primary phases:

1. Anagen (Growth Phase)

Anagen is the active growth phase, during which hair cells in the matrix rapidly divide and push up to form new hair. This is the longest phase, lasting from two to seven years, though the average is around three to five years. The duration of the anagen phase determines the maximum length a person's hair can achieve. Factors such as genetics, age, and overall health influence the length of this phase. Approximately 85-90% of all hairs are in the anagen phase at any given time.

2. Catagen (Transition Phase)

The catagen phase is a short transitional stage that marks the end of the active growth. It lasts for about two to three weeks. During this phase, the hair follicle shrinks, detaches from the dermal papilla, and hair growth ceases. The blood supply to the follicle is cut off, and the lower part of the follicle begins to degenerate. Only about 1-2% of hairs are in the catagen phase at any given time.

3. Telogen (Resting Phase)

Telogen is the resting phase, lasting approximately three to four months. During this period, the hair is fully formed but remains in the follicle, inactive. The old hair, now a club hair (characterized by a bulb-like end), is held in place by the follicle while a new hair begins to grow beneath it. Towards the end of the telogen phase, the new hair pushes the old club hair out, leading to natural shedding. It is normal to shed 50-100 telogen hairs per day. Approximately 10-15% of hairs are in the telogen phase.

Exogen (Shedding Phase)

Some scientists classify an additional phase, Exogen, as the period within the telogen phase where the old hair is shed. This phase is distinct from the resting period but is often considered part of telogen. During exogen, physical actions like washing, brushing, or combing can dislodge the old hair, making way for the new anagen hair.

Factors Influencing Hair Growth

Several factors can influence the rate and quality of hair growth, as well as the duration of each cycle phase:

• Genetics: An individual's genetic makeup largely determines hair type, thickness, and cyclical duration.
• Age: As people age, the anagen phase tends to shorten, and hair can become finer and less dense.
• Nutrition: A balanced diet rich in proteins, vitamins (especially biotin, vitamin D), and minerals (iron, zinc) is crucial for healthy hair growth. Deficiencies can impair the growth cycle.
• Hormones: Hormonal fluctuations, such as those during pregnancy, menopause, or due to thyroid conditions, can significantly impact hair growth and shedding patterns. Androgens, in particular, play a role in pattern hair loss.
• Stress: Both physical and emotional stress can disrupt the normal hair growth cycle, often leading to increased shedding (telogen effluvium).
• Scalp Health: A healthy scalp environment, free from inflammation or excessive buildup, is vital for optimal follicle function.
• Environmental Factors: Exposure to pollutants, harsh chemicals, and excessive UV radiation can damage hair and potentially affect follicle health. Watermans products are formulated to support optimal hair and scalp health.

Understanding the hair growth cycle provides insight into why hair loss or thinning can occur and how various interventions, like targeted nutrition or specialized haircare products, aim to support healthy hair production.

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Find these ingredients in Watermans products

• Biotin — you will find this ingredient in our Hair Growth Shampoo.
• Zinc — you will find this ingredient in our Hair Vitamins.