Hair Growth Cycle : Part 1

"Healthy hair growth is a continuous cycle, not a one-time event."

Most individuals think that their hair grows without stop in their whole life. However, it is important to note that hair follicles grow according to their growth cycle where different hair strands are at different stages of this process at any given point in time.

Having a proper knowledge of the hair growth cycle is very vital for any hair professional. No matter whether one gives hair treatment, hair replacements, scalp treatments or advises clients about hair fall; the knowledge about hair growth cycle will enable him to explain to his clients why hair falls, why some treatments need several months before they give their results, and when a professional help is required from a doctor.

This is because a proper knowledge about hair growth cycle enables hair professionals to have realistic expectations from their clients' treatment sessions.

1. What Is the Hair Growth Cycle?

2. The hair growth cycle refers to the natural cycle of producing, growing, shedding, and regenerating a hair follicle.

3. Whereas most animals shed all their hair at once during certain seasons, humans have a constant growth of hair. The hair follicle is independent from other hair follicles; each has its own unique growth cycle.

4. It is a way through which humans never shed all their hair simultaneously.

5. There are four phases in the hair growth cycle:

6. Anagen (growth phase)

7. Catagen (transition phase)

8. Telogen (resting phase)

9. Exogen (shedding phase)

 

The Four Stages of Hair Growth

1. Anagen Phase – The Growth Phase

Anagen Phase is the growth phase of the hair cycle.

In this phase, cells divide quickly in the hair bulb. Dermal papilla provides oxygen and nutrients. Hair grows constantly upward. Length of hair increases daily. It is the longest phase of the hair cycle.

Duration

Scalp hair – 2 to 7 years
Eyebrows - 1 to 2 months
Eyelashes - 1 to 2 months
The longer the hair stays in this phase, the more hair will grow.

Hair Growth Rate

On average, Hair grows 1 to 1.25 cm every month.
Around 12 to 15 cm per year.
Rates vary from person to person based on genetic make-up, age, nutrition, and general health condition.

Percentage of Hair in Anagen Phase

Normally, 85-90% of scalp hair is in the anagen phase.

2. Catagen Phase – The Transition Phase

The Catagen Phase represents a transitional phase between hair growth and resting.

During the catagen phase:

Hair stops growing. The hair follicle becomes smaller in size. There is separation between the dermal papilla and the hair bulb. Hair is not provided with any nourishment. Hair stays within the follicle but does not grow anymore.

Duration

About 2 to 3 weeks.
This phase is present in only 1-2% of the scalp hair.

3. Telogen Phase – The Resting Phase

Telogen Phase is a resting phase for the hair follicle. During this phase:

The follicle does not work. There is no hair growth. Existing hair still stays in the follicle. New hair starts to form underneath the resting hair. Even though the hair looks healthy, it is not growing anymore.
Duration

Usually 2 to 4 months.
About 10-15% of the scalp hair is in the telogen phase at one time.

4. Exogen Phase – The Shedding Phase

Exogen Phase is the last stage of the hair cycle.

During this phase: The old hair is naturally shed by the follicle. The new anagen hair slowly pushes out the old hair. This cycle continues. This is absolutely a normal process. Every day, the number of naturally shed hair is from 50 to 100. Only when people lose hair much more than regrow, hair loss is a problem.

• Daily Hair Loss

• It is very common for people to panic when they see hair on their pillows, brushes, or hair drain.

• Daily loss of hair is a natural occurrence.

• This happens because of the thousands of hair follicles that are in various stages of development, with some being shed while others keep growing.

• Normal shedding does not lead to baldness since hair is always replaced by new hair.

• Hair loss is caused by:

• Too many hair follicles entering the telogen stage.

• Destruction of hair follicles.

• Slowing of new hair growth.
  

The Hair Growth Cycle at a Glance

Factors That Affect Hair Growth

Several internal and external factors influence the health of the hair growth cycle.

1. Genetics

Genetics mostly influence the following features of hair:

• Thickness
• Density
• Texture
• Maximum length
• Hair fall pattern

Hereditary factors greatly contribute to hair growth.

2. Aging

With aging, the following characteristics appear:

• Reduced hair growth rate
• Shortened anagen phase
• Thinning of the hair
• Decreased pigmentation resulting in hair whitening

3. Diet

Hair growth depends on the appropriate nutrition. The following components are required for proper hair functioning:

• Proteins
• Iron
• Zinc
• Vitamin D
• Biotin
• Vitamin B12
• Omega-3 acids

Nutritional problems negatively impact the hair cycle.

4. Hormones

Changes in hormones have a considerable impact on hair growth. Such conditions as:

• Pregnancy
• Parturition
• Menopause
• Thyroid problems
• Polycystic Ovary Syndrome

Contribute to hormonal imbalance and hair fall.

5. Stress

Stress of physical and mental nature can shift a great amount of hair follicles into the telogen phase. This condition is called Telogen Effluvium, and it results in hair loss several weeks or months after the stressful period. Fortunately, hair regrowth usually occurs after the underlying factor is solved.

6. Medical Conditions

Specific medical problems can affect the natural hair growth cycle such as:

• Thyroid problems
• Immune system problems
• Anemia
• Scalp problems
• Other diseases

Medical evaluation is necessary when there is unexpected hair loss.

7. Medications

Hair loss can be caused by specific drugs. These drugs can be:

• Cancer treatments (chemotherapy)
• High blood pressure
• Depression
• Blood thinners
• Hormones

The client should contact his doctor before discontinuing the use of the drug.

Hair Growth in Different Parts of the Body

Not all body hair grows at the same rate.

This is why scalp hair can grow much longer than eyebrows or eyelashes.

Common Misconceptions About Hair Growth

Misconception 1: Cutting hair promotes faster hair growth.
Factual Truth: Cutting eliminates the dead tips but has no effect on the hair follicle or hair growth rate.

Misconception 2: Shaving makes hair thicker.
Factual Truth: Shaving results in the formation of blunt ends, making the re-growing hair appear coarser. However, it does not make the hair thicker.

Misconception 3: Shampooing frequently leads to hair loss.
Factual Truth: Shampooing facilitates the elimination of hairs that have already entered the shedding process. It does not result in hair loss.

Misconception 4: Hair oil accelerates hair growth.
Factual Truth: Hair oil nourishes the hair shaft and the scalp. It does not affect the hair growth rate.

Reasons Why the Process of Hair Growth Knowledge Is Necessary For Hair Care Professionals:

Knowledge of hair growth process helps hair care professionals to:

Provide explanation of hair loss in normal circumstances to the clients.

Be able to distinguish between normal hair shedding and hair loss.

Advise on proper hair care regimen.

Set realistic expectations regarding hair care procedures.

Schedule hair transplantation services properly.

Know the time required for recovery from hair transplantations.

Realize the necessity of consultation with dermatologist or trichologist.

Professional knowledge gives clients confidence.