The Hair Growth Cycle

Understanding the Hair Growth Cycle

Every strand of hair on your head undergoes a continuous process of growth, transition, and rest. This cyclical phenomenon, known as the hair growth cycle, is fundamental to understanding hair health, growth, and loss. Each hair follicle operates independently, meaning that at any given time, different hairs are in different stages of their respective cycles.

The Anagen Phase: Active Growth

The anagen phase is the active growth period of a hair follicle. During this stage, cells in the hair bulb divide rapidly, forming new hair cells. These cells then push upward, creating a new hair shaft that emerges from the scalp. This is the longest phase of the hair growth cycle, typically lasting between two and seven years, though its duration can vary significantly based on genetics, age, and body location. For instance, the anagen phase for eyebrow hairs is much shorter than for scalp hair.

Factors influencing the length of the anagen phase directly impact hair length. A longer anagen phase allows hair to grow longer, while a shorter anagen phase results in shorter hair. Approximately 85-90% of all scalp hairs are in the anagen phase at any given time.

The Catagen Phase: Transition and Regression

Following the anagen phase, hair enters the catagen phase, a short transitional period lasting about two to three weeks. This phase marks the cessation of active hair growth. During catagen, the hair follicle shrinks, detaches from the dermal papilla (the structure supplying blood and nutrients to the hair follicle), and moves upwards towards the surface of the scalp. The lower part of the hair follicle begins to disintegrate, and the hair shaft itself stops growing. Only about 1% of scalp hairs are in the catagen phase at any given time.

The Telogen Phase: Resting and Shedding

After the catagen phase, hair follicles enter the telogen phase, the resting phase. This phase typically lasts for about two to four months. During telogen, the hair follicle is completely at rest, and no active growth occurs. The hair bulb at the base of the hair shaft is fully keratinized, meaning it is hardened and ready to be shed. At the end of the telogen phase, the old hair is shed, and a new hair begins to grow from the same follicle, initiating a new anagen phase.

It is normal to shed between 50 and 100 hairs per day as part of this natural cycle. This shedding is often aided by daily activities such as brushing or washing hair. Roughly 10-15% of scalp hairs are in the telogen phase at any given time.

Exogen Phase: The Shedding Process (Sometimes Considered a Separate Phase)

While often considered part of the telogen phase, some trichologists identify an exogen phase as the active shedding of club hairs (hairs that have completed their growth and are ready to be shed). This is the period when hair naturally detaches and falls out. It's the final step before the follicle re-enters the anagen phase to begin growing a new hair.

Normal Hair Cycling vs. Hair Loss

Understanding the hair cycle is crucial for distinguishing between normal hair shedding and patterns of hair loss. When the balance of the hair cycle is disrupted, it can lead to various forms of alopecia (hair loss).

Cycle Phase	Duration on Scalp	Percentage of Hairs	Key Event Production
Anagen	2-7 years	85-90%	Active growth
Catagen	2-3 weeks	1%	Follicle shrinks; growth stops
Telogen	2-4 months	10-15%	Resting; shedding of old hair

Factors Influencing the Hair Cycle

Several factors can influence the duration and equilibrium of the hair growth cycle:

• Genetics: Genetic predisposition plays a significant role in determining how long each phase lasts and the overall density of hair.
• Age: As people age, the anagen phase tends to shorten, and hair follicles may miniaturize, leading to finer, shorter hairs.
• Hormones: Hormonal fluctuations, such as those experienced during pregnancy, puberty, or menopause, and conditions like thyroid imbalance, can significantly impact the hair cycle. Androgens, in particular, are strongly linked to pattern hair loss.
• Nutrition: A balanced diet rich in essential vitamins, minerals, and proteins is vital for healthy hair growth. Deficiencies can disrupt the cycle, leading to increased shedding or slower growth.
• Stress: High levels of physical or emotional stress can prematurely push a large number of hairs from the anagen phase into the telogen phase, leading to a noticeable increase in shedding several months later, a condition known as telogen effluvium.
• Medications: Certain medications can have side effects that impact hair growth and loss.
• Health Conditions: Underlying medical conditions, autoimmune diseases, and scalp infections can disrupt the normal hair cycle.

Maintaining a Healthy Hair Cycle

Supporting a healthy hair cycle involves a holistic approach. While topical treatments and specific hair products can provide external benefits, internal health is paramount.

• Balanced Diet: Consume a diet rich in proteins, iron, zinc, biotin, and vitamins A, C, D, and E. These nutrients are essential for keratin production and overall follicle health.
• Stress Management: Implement stress-reduction techniques such as meditation, yoga, or regular exercise to minimize the impact of stress on your hair.
• Gentle Hair Care: Avoid harsh chemical treatments, excessive heat styling, and tight hairstyles that can damage hair and follicles. Use a gentle shampoo and conditioner to maintain scalp and hair health.
• Regular Scalp Stimulation: Massaging the scalp can increase blood flow to the hair follicles, potentially supporting nutrient delivery and promoting a healthy environment for growth.

Consulting with a specialist can help identify specific disruptions to your hair cycle and recommend targeted strategies to address them. Early intervention is often key in managing cyclical hair issues and promoting healthy, consistent hair growth.

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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.