The Hair Growth Cycle

For many people, the hair on their head directly expresses their personality.

However, hair on other parts of our bodies can have mixed reviews and be

welcome or unwanted. Therefore, it’s helpful to understand the hair growth

cycle in order to recognise, understand and address any problems you may

encounter with your hair.


On a practical level, our hair provides us with protection. A full head of hair shades

our scalp from the harmful rays of the sun, and eyelashes and eyebrows keep dust,

dirt and sweat out of our eyes. Even the hairs in our nose and ears help to keep out

germs and other foreign objects. Body hair helps regulate our body temperature: The

hairs stand up when it’s cold, keeping any warm air close to the body – like a

warming duvet. But aesthetically, we may not want some of this hair and may wish to

shape or remove it, so we feel more confident in our daily lives.

Let’s look at the different types of hair on our bodies and how it grows.


Types of hair

Apart from the palms of our hands or soles of our feet, hair covers the entire surface

of our body. We have short fine 'vellus' hairs (peach fuzz) on the body and longer,

thicker 'terminal' hairs on your head, face, eyelashes, eyebrows, pubic area, chest

and belly.


How much of each hair type you have varies from person to person. It depends on

your gender (and thus hormones), age, and medical conditions. Children have

mostly vellus hair, whilst terminal hair accounts for 30 per cent of a woman's body's

surface and 90 per cent for men.


Some medical conditions and treatments can affect our natural hair growth. Either by

upsetting the natural balance of hormones or altering one of the hair growth stages.

Polycystic ovary syndrome (PCOS) and menopause are two conditions that can affect our hair. Please read our blog articles to learn more about them.


Hair structure and growth

Hair is made of a tough protein called keratin. The hair shaft is anchored within the

skin by the hair follicle, a sheath of skin and connective tissue surrounding the hair

root. The base of the root is bulbous in shape (hair bulb), and it is here that living

cells divide and grow to build the hair shaft. Blood vessels (within the dermal papilla)

nourish the cells in the hair bulb and deliver hormones that modify hair growth and

structure at different times of life.


Because new cells keep attaching to the hair from its base, it is gradually pushed up

out of the skin. In this way, a single hair on your head grows at a rate of about 0.3-

0.4 mm/day or 15 cm (6 inches) per year. But why is facial hair, and especially

eyelashes, eyebrows, and body hair shorter than the hair on your head?


The answer lies in the hair growth cycle.


Hair growth cycle

Depending on what literature you read, the hair growth cycle is composed of three to five phases. Because there is an overlap between consecutive phases they are often grouped together. Each phase has its own timeline, which is affected by your genes, age, nutrition, and overall health.


The stages of hair growth are known as the anagen (growing phase), catagen (transition phase), telogen (resting phase) and exogen (shedding phase) and the early anagen phase. Let’s look at these in a bit more detail.


Early Anagen and Anagen (Growing phase)

The anagen phases are active phases of hair growth. The cells in the root of the hair are dividing rapidly and the new hair develops. The ‘old’ hair (also known as club hair) has been shed during the exogen phase and the new hair in the early anagen phase has room to grow up the follicle and eventually out through the skin.


The length of the anagen phase determines how long the hair grows. Scalp hair can stay in this active phase of growth for two to six years and thus can achieve quite a length before it sheds.


You may have noticed that you have difficulty growing your hair beyond a certain length compared to friends because you have a shorter anagen phase of growth.


In addition, approximately 90 per cent of the hairs on our head are in some part of the anagen growing phase at any one time. Thus, we can maintain a regular hairstyle, without it suddenly looking different overnight. Because, although hair follicles act independently of each other, the majority are in the same phase.


However, the hair on the arms, legs, eyelashes, and eyebrows has a very short anagen phase of about 30 to 45 days, explaining why they don’t grow as long as the hair on your head. And to be honest, I think we’re all glad of that.


Another important part of the anagen phases gives your hair its colour. Initially, hair is white. It gets its natural colour from a type of pigment called melanin. As the hair forms in the follicle, melanocytes inject melanin into the keratin cells. Thus, hair in the early anagen phase contains abundant melanin.


Catagen (Transition phase)

The subsequent growth cycle phase is the catagen, a short transitional period in which the hair stops growing. It pulls away from the bottom of the hair follicle, thus losing its nutrient supply from the dermal papilla.


Approximately 3 per cent of all hairs are in the catagen phase at any time. On average, this phase lasts for about one to two weeks. This phase forms what is known as club hair, a hair that remains in place but no longer receives nutrients to grow.


Telogen (Resting phase)

The next phase of the growth cycle is the telogen or resting phase. During this phase, the club hair sits inactive, and the hair follicle attaches once more to the dermal papilla, ready to start the anagen phase again.


Usually, 6 to 8 percent of all hairs are in the telogen phase. This phase lasts for about three months for hairs on the head and longer for eyelashes, eyebrows and arm and leg hairs. Pulling out a hair during this phase will reveal a solid, hard, dry, white material at the root.

During telogen, there is very little or no melanin in the follicle.


Exogen (Shedding phase)

Some experts describe the telogen phase as the resting and shedding phase. Others mention the shedding phase separately, known as the exogen phase.


The exogen phase is an extension of the telogen phase and occurs as new hair starts to grow at the base of the follicle. The new growth pushes the club or ‘old’ hair up and out of the follicle and the hair sheds.


The exogen phase can last between two and five months.


The new hair now enters the early anagen phase and the cycle starts again.


How does the hair growth cycle affect hair removal?

Knowing a little more about the hair growth cycle helps us to understand why some hairs appear to grow back more quickly than others after shaving or perhaps waxing. The cycle also explains why we need repeated treatments to achieve more permanent hair removal results with IPL or electrolysis.


Intense Pulsed Light (IPL)

IPL treatment relies on the absorption of light by the hair pigment (melanin). Therefore, the most effective treatments are with hair containing more melanin.


As mentioned above, the hair and the follicle contain most melanin during the early anagen (active growing) phase. Thus, we must repeat an IPL treatment several times to catch the resting hair follicles as they re-enter the growth phase.


Learn more about IPL treatments at our Central London salon in our blog article and treatment page.


Electrolysis

Electrolysis treats hair effectively in the active growth stage, the early anagen and anagen phase only.


As the hair actively grows, it remains connected to the dermal papilla. Electrolysis can therefore destroy the dermal papilla, preventing further hair growth and achieving permanent hair removal.


But remember, hair grows at different rates and can be in different growth stages on other parts of the body. Therefore, it’s important to have regular treatments to treat all hairs during the anagen phase.


Learn more about electrolysis treatments at our City of London salon on our treatment page.


If you feel that you’re losing hair faster than you’re used to, or have excessive hair growth, talk with your doctor. An underlying condition that’s disrupting the stages of hair growth may be to blame. Treating it promptly may help manage the problem.

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