We spend so much time thinking about our hair — how to style it, how much of it we have, how many greys have started showing up... but how often have you thought about its true purpose?
Bloodhound Gang said it best: we ain't nothin' but mammals. As members of the mammal family, we need hair for some very specific reasons, including: regulating our body temperature, keeping our skin hydrated by protecting its oils, dispersing pheromones, and protecting us from the sun [1].
So with all these jobs to do, it's no wonder the hair growth cycle is made up of some complex stages. By understanding the stages of hair growth we can look after our hair better (and keep it around for longer).
How long is the hair growth cycle?
Every hair follicle you have is a mini organ (not the musical kind), with its unique life cycle [1]. Wild, right?
Hair grows through a process that happens in the follicles. Special skin cells interact with stem cells and kickstart hair growth. When these stem cells decide to become part of a hair follicle, they multiply —eventually leading to the creation of a mature hair follicle [2].
There are a bunch of steps involved as the cells grow, change, turn a new colour, and even die!
On average, the human hair cycle lasts just over 5-6 years. This happens in 4 stages: the anagen phase, catagen phase, telogen phase, and exogen phase [2].
If we're breaking it down further, scientists say hair grows about 0.35 millimetres per day. Or, around 6 inches per year.
It should be noted that how fast your hair grows can also depend on your cultural background — for example, people of Asian or African descent usually find their hair grows faster (around 5-20mm per month) [3].
When it comes to hair growth, it can be slow but not steady — because of all the different stages it has to go through, it will look different for everyone [3].
Hair growth cycles also look different for different areas of the body. For example, those almost-invisible vellus hairs on your face, eyebrow hairs, pubic hair, or other body hair will all grow at different rates to scalp hair [4].
1. Anagen phase: Growth
The first stop on the hair growth train is the anagen phase.
Think of your hair follicle as a cylindrical structure that contains a bunch of different layers. At the very end of this cylinder (the bit that's underneath your skin) is what's called a bulb [4].
The anagen phase is the most active growth phase in the hair cycle. Cells at the bottom of the hair follicle, near the bulb, start dividing really quickly — leading to new hair growth.
Each hair bulb on your head keeps pushing out its hair for the entire anagen phase until it's then cut off or falls out [4].
This is the longest stage of the growth cycle, lasting 3-7 years depending on your genetics and background. Most of the hairs on your head right now are in their anagen phase [4].
2. Catagen phase: Transition
Next up is the catagen phase, where hair transitions from its active growth phase to resting.
This happens immediately after the anagen phase ends — hair follicles begin to shrink and hair growth slows down [4].
During the catagen phase, the hair gets cut off from the blood supply and cells at the bottom of the follicle. Then it separates from the hair bulb but stays put before moving into the telogen phase.
In total, the catagen phase usually lasts for around 10 days [4].
3. Telogen phase: Resting
After all that hard work it's time for your hair to take a beat — and move into its resting phase. The telogen or resting phase is when hair growth stops, but doesn't quite start falling out [4].
Even though it's a time of rest, new hairs actually start forming during the telogen stage. These new hairs start appearing inside the follicles that have let go of their old hair strands during the catagen phase [4].
The telogen phase usually lasts for about 3 months for most people and involves approximately 10-15% of your scalp hair at any given time.
In the past, researchers considered this to be the final phase of the cycle. But now we know there's a new guy on the block: the exogen phase [4].
4. Exogen phase: Shedding
The final stage of the cycle is also known as the shedding phase and is pretty much what it sounds like. The hair begins to fall away from the scalp so that a new hair growth cycle can start [4].
This stage usually lasts anywhere from 2-5 months — hair shedding looks different for everyone, but people can lose up to 100 hairs a day in the exogen phase and it's still considered normal [4].
Hair shedding sounds scary, but it's important to remember there are usually new hair follicles locked and loaded, ready to burst through as the old hair falls out.
What factors disrupt the hair growth cycle?
You've got the cycle bit down, so what happens if something gets in the way of healthy hair growth? There's a number of factors that might stop the hair growth cycle from doing its thing, including:
Ageing
As we get older, we start to experience more hair thinning. New hair growth slows down and eventually stops completely for some people [3].
Hormones
For both men and women, hormones can play a huge role in hair health. Pregnancy hormones can cause increased hair growth, whereas imbalances in some male sex hormones (like testosterone) can cause hair loss [3].
Stress and illness
No shockers here, but stress and illness can definitely interrupt the hair growth cycle. According to scientists, being stressed or sick can shift your hair follicles back into the resting phase when they should be growing.
Even something like being on a diet that's too restrictive or other nutrient deficiencies (e.g. low iron) can cause your hair to stop growing [3].
Medication side effects
Some medications might interrupt your hair growth or cause hair loss. An example is chemotherapy medicines, which can cause sudden hair loss affecting your whole scalp.
Other medicines like lithium, certain amphetamines, and beta-blockers can also cause hair loss.
If you're concerned about medication side effects, always chat with your doctor or healthcare professional [5].
The link between hair loss and the hair growth cycle
No matter what the cause is, if your hair growth cycle is disrupted it can definitely lead to hair loss or thinning. Hair fall can happen faster than your scalp grows new hair, leading to your hair appearing thinner [5].
There are specific conditions that cause hair loss and/or an interrupted hair growth cycle, including:
- Telogen effluvium. This happens when you've been through a major stressful event or illness. Hair might start falling out in moderate amounts, and appear thinner on the scalp. This condition is reversible and doesn't usually lead to permanent hair loss.
- Androgenetic alopecia. This is a genetic condition that's hereditary and usually starts to happen with ageing and hormonal changes. It's often referred to as male pattern baldness, as it follows a common pattern on the scalp — e.g. receding hair line, or thinning hair on top of the scalp.
- Alopecia areata. This is an autoimmune disease that can cause hair to fall out in patches. It usually shows up for people who have other autoimmune diseases or chronic conditions.
- Traumatic alopecia. It's all in the name; this occurs when something traumatic happens that stops hair growth. It could be damaging hair with extreme heat/hot styling tools, using chemicals such as bleach or hair dye, or pulling hair into styles that are too tight for the scalp [5].
All of the above conditions and factors impact the anagen or growth phase. When this phase is too short or interrupted too soon, more hairs will go into resting phase, and then move on to shedding.
The hairs also won't stay in the anagen phase for enough time to grow longer [5].
If you're experiencing hair loss and need some advice, or you've noticed excessive shedding, it might be time to get some help. Pilot's team of hair experts and health practitioners can find a solution that's tailored to your needs — whether it's medical treatment or a new haircare routine to prevent hair loss.
Whether you've been noticing extra hair on the shower floor for a while, or it's only just started happening — we're here to help.
How to keep your hair healthy through each phase
There are many ways you can improve your hair health as it goes through its cycles.
This includes minimising your stress levels as much as you can (book that golf day in!), eating a healthy diet, and staying on top of any medical conditions [5].
If you're someone that loves a bleach session or a perm, it might be time to go natural. Staying away from hair dryers and other hot tools can also help to keep hair healthy.
And if it's dandruff or other itchy things going on, treating them as soon as possible will make sure your hair can get back to doing its thing [5].
If it's genetics and/or ageing that's the cause, there's still options available. Chat to a health professional about your options for hair loss, and they might recommend some different treatments to try.
The long and short of it (no pun intended) is: hair loss is incredibly common, and you're not alone. So don't wait to get some support and advice if you need it.
Image credit: Pexels/Diva Plavalaguna
.svg)
