Here’s how factors like your age, ethnicity and even the time of year influence your hair’s growth.
If you’ve recently gotten a bad haircut, you’re probably wondering one thing: how fast does hair grow?
The answer, unfortunately, is a complicated one. The speed of hair growth on your scalp depends on a multitude of different factors. There is no universal answer, as it all depends on how old you are, your race, your diet, and even your hormones.
If you’re perfectly healthy, at the right age, and aren’t going through stress, however, scientists have argued that there is a standard rate at which hair grows which changes across different races.
How fast does hair grow?
Healthy human hair typically grows at a rate of 0.35mm a day, or 0.014 inches. This means your hair grows 2.45mm (0.1 inches) in a week, and 12.775cm (5 inches) every year.
However, according to studies, your growth may be influenced by ethnic and geographical origin.
It should be noted that the above hair-growth rates will not be the same for everyone. A variety of different factors come into play when it comes to growing your hair longer.
Age has a big influence when it comes to hair growth rates. Your hair will grow slower and thinner as you get older, with some follicles dying off which can lead to baldness.
Hormones affect hair growth, too. It’s known that during pregnancy women can grow hair more quickly and it comes in thicker due to a rise in estrogen. Your hair can also grow back differently after chemotherapy.
Stress levels and illness/wellness can reduce your hair’s growth rate also. This includes, according to a StatPearls journal published by the National Library of Medicine, a reduced rate of hair growth and even alopecia/acute hair shedding after and during “febrile illness, severe infection, major surgery, severe trauma, postpartum hormonal changes, particularly a decrease in estrogen, hypothyroidism, discontinuing estrogen-containing medication, crash dieting, low protein intake, heavy metal ingestion, and iron deficiency.”
What are the hair growth stages?
Each hair follicle goes through three phases: anagen, catagen, and telogen.
- Anagen. The phase is when an individual hair grows quickest and typically lasts up to four years for each follicle
- Catagen. This phase takes place when the hair stops growing.
- Telogen. This is where your hair stops growing to let in new hair.
In a normal healthy person’s scalp, about 85 per cent of hairs are anagen hair and 15 per cent are telogen hair.
According to researchers at the Sampson Regional Medical Center in the US, a hair follicle usually grows anagen hair for almost four years, then rests for about four months. A new anagen hair begins to grow under the resting telogen hair and pushes it out. This is when we lose hair.
If there is some kind of stress to the body it can cause 70 per cent of anagen hair to precipitate into the telogen phase thus causing hair loss.
It’s not just illness, stress or changing hormones that can cause an increase in catagen or telogen hair.
According to the British Journal Of Dermatology, the seasons have a say in hair growth rates. The study posited that “the number of shed hairs reached a peak around August/September, when least follicles were in anagen”.
Read more:
- What causes hair to turn grey?
- Why don’t people have naturally blue or green hair?
- Why is curly hair curly?