Understanding the Hair Growth Cycle: Why Hair Grows, Rests and Falls Out

Hair is constantly changing. Even when it looks like nothing is happening, thousands of hair follicles across the scalp are independently growing, resting, shedding and preparing to grow new hair.

This process is known as the hair growth cycle.

Understanding this cycle is particularly important when dealing with hair loss. Increased shedding does not necessarily mean that the hair follicle has stopped producing hair. In many cases, it means that the normal balance between the different phases of the hair cycle has been temporarily or progressively altered.

So what actually happens beneath the scalp?

Hair Does Not Grow Continuously

Each hair develops from a structure in the skin called the hair follicle. Rather than continuously producing the same hair indefinitely, the follicle repeatedly passes through periods of activity and rest.

The hair cycle is generally divided into four stages:

Anagen – active growth
Catagen – transition
Telogen – rest
Exogen – shedding

Each follicle operates independently. This is important because it prevents all of our hair from growing and falling out at the same time.

At any given moment, most scalp hairs are actively growing, while a smaller percentage are transitioning, resting or preparing to shed.

1. Anagen: The Growth Phase

Anagen is the active phase of the hair cycle and, under normal circumstances, the phase in which most scalp hairs are found.

During anagen, cells inside the hair follicle divide rapidly and produce the keratin that forms the hair shaft. The hair continues to grow as long as the follicle remains in this active state.

For scalp hair, the anagen phase can last for several years. This is one of the main reasons some people can naturally grow considerably longer hair than others: their follicles may remain in the growth phase for longer.

Approximately 85% of the hair on the scalp is normally in the anagen phase. Hair grows at roughly 1 centimetre per month, although growth speed varies between individuals.

The duration and quality of this phase can be influenced by several factors, including:

• genetics

• age

• hormonal activity

• nutritional status

• general health

• stress and illness

• the condition of the scalp and hair follicle

In certain forms of hair loss, the growth phase can gradually become shorter. The follicle spends less time producing a strong, mature hair before moving into the next stage.

2. Catagen: The Transition Phase

After years of active growth, the follicle enters the much shorter catagen phase.

Catagen is essentially a transition period.

Hair growth stops, cellular activity in the follicle decreases and the lower part of the follicle begins to shrink. The hair separates from the structures that supported its active growth but remains temporarily anchored inside the follicle.

This phase usually lasts only a few weeks and involves a very small percentage of scalp hairs at any particular moment. DSD de Luxe estimates approximately 1% of hair to be in the catagen phase under normal conditions.

The follicle is now preparing for a period of rest.

3. Telogen: The Resting Phase

The next stage is telogen.

During telogen, the follicle is relatively inactive and the existing hair is no longer actively growing. However, it can remain in the follicle for several months before eventually being released.

A normal telogen phase generally lasts around three to four months.

This delay is extremely important when trying to understand hair loss.

A stressful event that occurs today may therefore not cause visible shedding tomorrow. Hair affected by that event may first move prematurely out of the growth phase and into the resting phase. Increased shedding might only become noticeable several weeks or months later.

This is why identifying the cause of sudden hair shedding often requires looking backwards rather than only considering what is happening at the present moment.

Possible triggers can include significant physical or emotional stress, illness, hormonal changes, nutritional deficiencies or other changes within the body.

4. Exogen: The Shedding Phase

Exogen describes the stage in which the resting hair is finally released from the follicle.

This is the hair that you may notice:

• in the shower

• on your brush

• on your pillow

• on your clothes

• when running your fingers through your hair

Shedding itself is therefore a normal part of hair renewal.

At the same time, a new hair can begin developing within the follicle. The follicle returns to the anagen phase, and a new growth cycle begins.

The old hair is released, the new hair takes its place, and the process repeats.

So Why Does Hair Sometimes Start Shedding More?

Normally, the different stages of the cycle remain relatively balanced.

Problems become noticeable when that balance changes.

For example, if an unusually large number of follicles enter the telogen phase at approximately the same time, considerably more hair may begin shedding several months later. This type of diffuse shedding can occur after certain physiological or emotional stressors.

Hair loss can also develop differently.

In androgenetic alopecia, for example, genetically and hormonally susceptible follicles gradually become smaller. Over repeated hair cycles, the hairs they produce can become progressively finer, shorter and less visible.

This is one reason why simply noticing that “hair is falling out” does not tell us exactly what is happening.

The pattern of hair loss, condition of the scalp, diameter of individual hairs, duration of shedding and medical history can all provide important information.

Why Hair-Loss Results Take Time

The biology of the hair cycle also explains one of the most frustrating aspects of treating hair loss:

hair changes are slow.

A follicle that has spent several months in its resting phase cannot instantly produce centimetres of new visible hair.

Even when the factors contributing to excessive shedding are addressed, the follicle must transition back into active growth. New hair then needs time to emerge from the scalp and become long enough to noticeably contribute to hair density.

This is why hair-loss routines are usually evaluated over months rather than days or weeks.

DSD de Luxe's anti-hair-loss treatments are also developed with the hair cycle in mind, with several formulas designed to support follicular activity and help maintain the anagen growth phase.

Consistency is therefore particularly important.

Changing products every few weeks because visible new growth has not yet appeared can make it difficult to properly evaluate whether a routine is working.

Hair Shedding vs. Hair Loss

Another useful distinction is the difference between shedding and progressive hair loss.

Seeing hairs fall out does not automatically mean that the follicle is permanently damaged.

Temporary shedding can occur when a higher percentage of follicles enter the resting stage at the same time. If the follicles remain healthy, they can subsequently return to anagen and produce new hairs.

Progressive conditions can behave differently. The follicle itself may gradually change over successive cycles, producing increasingly thinner hairs.

Some warning signs worth paying attention to include:

• significantly increased shedding that continues for several months

• progressively reduced hair density

• widening of the hair part

• increasing scalp visibility

• recession of the frontal hairline

• noticeable differences in hair thickness

• clearly defined patches of hair loss

• scalp inflammation, itching, scaling or discomfort

These patterns can have very different causes and may require different approaches.

Why Scalp Health Matters

Hair growth takes place inside the follicle, which means hair care should not focus exclusively on the visible hair shaft.

The condition of the scalp and follicular environment also matters.

Excessive sebum, persistent dandruff, inflammation or other scalp conditions can affect scalp health and should be appropriately managed. A complete approach to hair care therefore considers both the hair and the scalp from which it grows.

At DSD de Luxe, this relationship between scalp health, follicular activity and hair quality forms the basis of our trichological approach to hair care.

Understanding the Cause Comes First

There is no single explanation for every type of hair loss.

Genetic predisposition, hormonal changes, stress, nutritional factors, medical conditions, scalp disorders and other influences can all affect the hair cycle differently.

That is why an accurate assessment is particularly valuable when hair loss becomes noticeable or persistent.

During a professional hair diagnosis, factors such as medical and family history, hair-care habits, the condition of the scalp and the characteristics of individual hairs can be evaluated. Trichoscopy can provide a magnified view of the scalp and follicles, helping to identify patterns that may not be visible to the naked eye.

Understanding why the hair cycle has changed makes it possible to choose a much more targeted approach.

The Hair Cycle Never Really Stops

Growth. Transition. Rest. Shedding. And growth again.

The hair cycle is a continuous biological process taking place across thousands of individual follicles every day.

Some shedding is therefore completely natural. What matters is maintaining a healthy balance between hair that is leaving the scalp and new hair that is growing to replace it.

When that balance changes noticeably, understanding the hair cycle can help explain what is happening — and why restoring healthy hair density requires patience, consistency and, when necessary, an appropriate professional diagnosis.