Hair Growth Cycles: How Does Hair Grow?
For decades, a group of scientists have been asking one simple question:
How does hair grow?
The answer, they’ve discovered, isn’t straightforward. But while there’s plenty of research still to be done, they’ve figured out the basics.
There are 3 main stages of hair growth. That is, your hair goes through phases of growth, rest, and shedding before coming full circle back to growth. This process is called the hair growth cycle.
In understanding the science around hair growth, we can start to understand what impacts hair growth, what may cause hair loss, and what we can do to treat it.
The 3 Stages of Hair Growth
Your hair follicles don’t operate in tandem and they’re not synchronised. Every single hair follicle is at its own stage in the hair growth cycle.
If they were synchronised, you’d lose the whole head of hair in one go and have to regrow it from scratch.
So how does hair grow? In three stages:
Anagen Growth Phase
It’s the phase we all crave — the active period of follicle growth that results in long, healthy hair.
About 90% of the hair on our head is in the anagen growth stage at any given time. However, that number tends to decline with age.
During the anagen stage, there are tiny bulb cells called keratinocytes inside the hair follicle that are rapidly proliferating to form a strong and flexible hair shaft.
The anagen phase is often split up into two stages called proanagen and metanagen. What we’ve described above — the proliferation of cells — is the proanagen phase.
The second phase, metanagen, is when the hair shaft appears on the surface of the skin.
The anagen stage for scalp hair lasts anywhere from 3 to 6 years. The length of the phase determines how long your hair can grow before it falls out. So if you’re struggling to pull off the Rapunzel look, chances are you have a shorter anagen phase.
So what about body hair?
Hairs on your arms and legs, as well as eyelashes and eyebrows, have much shorter anagen phases of just 30–45 days. That’s why they never grow too long.
Catagen Transition Phase
From the anagen phase, your hair transitions into the short-lived catagen stage. About 1% of your scalp hairs are in this phase at any given time.
While the catagen phase only lasts a week or so, a lot happens.
The hair follicle rapidly degenerates. Cells in the follicle no longer proliferate. In fact, they undergo apoptosis or ‘programmed death’.
The hair shaft separates from the hair follicle and is cut off from any blood supply. It stops growing and shrinks, losing about one-sixth of its standard diameter.
One thing that doesn’t usually happen in the catagen phase is hair shedding. That’s right. Old hair usually only sheds when new growth pushes it out. And new growth doesn’t occur during the catagen phase.
By the end of the catagen phase, the hair follicle has become dormant as it enters the final phase of the hair growth cycle: the telogen phase.
Telogen Resting Phase
Your hair follicle has clocked off and is having a much-needed break. During the telogen phase, the follicle is completely at rest. At any given time, about 10–15% of your scalp hair is in this stage, which lasts about 100 days.
Many people divide the telogen stage into two parts. The first is what we’ve already described.
The second is the exogen phase, which could be considered the shedding stage. During exogen, new hair starts to form in the follicle and pushes the old hair shaft out, completing the hair growth cycle. It’s normal to lose anywhere between 50 and 100 telogen hairs each day.
What Can Disrupt the Hair Growth Cycle?
If your hair growth cycle is disrupted, you may start to experience hair thinning and hair loss. Many things can influence the hair growth cycle, with some of the strongest factors including:
- Hormonal fluctuations
- Vitamin deficiencies
- Scalp inflammation
Sometimes the anagen phase is cut suddenly short as your body goes through severe stress — for example, from an accident, an illness, restrictive dieting, or a sudden trauma.
This type of hair loss is called telogen effluvium and it’s triggered when many hair follicles prematurely enter the telogen phase. Once those hairs enter the final exogen phase, about 3 months after the sudden trauma, you may notice sudden, diffuse hair loss all at once.
Hormones can also have a strong influence on the hair growth cycle. Take pregnancy hair loss.
During pregnancy, women can experience a prolonged anagen phase. This means a lot of hair follicles transition to the catagen phase all at once postpartum when oestrogen levels drop. The result appears to be more hair fall than usual.
The Hair Growth Cycle and Male Pattern Baldness
The most common type of hair loss is male pattern baldness, a hereditary type of hair loss that’s characterised by a receding hairline and a balding crown.
Male pattern baldness happens when a combination of genes and hormones affects the hair growth cycle.
To keep it simple, male pattern baldness begins when the anagen phase starts to produce fewer hairs to replace those that are falling out. The catagen and telogen phases usually remain the same.
Fortunately, most types of hair loss, including male pattern baldness can be treated.
A Hair Loss Treatment Made for You
If you suspect your hair growth cycle has been disrupted, there’s nothing to worry about.
To begin with, it’s completely natural for your anagen cycle to shorten over time. Many people experience less hair growth and more hair loss as they age.
More importantly, if you spot hair loss early, it can be stopped. It could even be reversed.
The Hairy Pill® is a specific, personalised treatment for men’s hair loss and women’s hair loss. Invented by world-renowned dermatologist Professor Rodney Sinclair, the underlying technology has been tested, patented, and clinically proven.
And the best bit?
It’s just one pill, taken daily. It can be ordered from the comfort of your couch and delivered to your door. Start the treatment now.