How does hair grow?
Hair, which is made of keratin and has three layers, begins growing
from the root (papilla) at the base of a hair follicle. The inner layer
is the medulla, the second layer is the cortex and the outer layer is
the cuticle. The roots are made up of protein cells and blood. The blood
vessels in the scalp feed the root to create more cells and make the
hair grow. Hair actually gets pushed up through our scalp near the
sebaceous glands, which add oil (i.e. sebum) to the hair and keeps it
moisturized. Hair is dead by the time it reaches your scalp. We are born
with all of the hair follicles we will ever have and that are around 5
million on our entire body with 1 million just on our heads. This means
there is no way to increase the density of your hair.
Three Hair Growth Cycles
- Anagen phase – the active phase is where the cells in the root of
the hair divide rapidly and grows about 1 cm. every 28 days. Scalp hair
is in this phase of growth for 2 to 6 years.
- Catagen phase – when the scalp transitions from anagen phase your
hair enters the catagen or transitional phase, and only about 3% of all
hairs are ever in this phase at any given time. This phase lasts about 2
to 3 weeks where growth stops.
- Telogen phase – this is the last phase and resting phase when your
hair is released and falls out. About 6% to 8% of all hairs in this
phase at any given time. There are about 25 to 100 telogen hairs that
are normally shed each day. The hair follicle that remains will be
inactive for three months before the entire process is repeated.
How fast does hair grow?
Ah, the question we all are dying to know the answer to! The most
commonly accepted statistic is
that hair on the scalp grows about .3 to .4 mm/day or about 3-6 in. per year. But the truth is, as with all things hair and health related, the answer is: it depends. “The rate of growth can be influenced by any number of variables,” Elizabeth Cunnane Phillips, a trichologist at the Philip Kingsley Clinic told Huffington Post. Those variables include “health, dietary habits, and endocrine function including thyroid, low iron or anemia…All of these have the capacity to influence hair growth and loss cycles.”
In a study conducted between 1999 and 2003, 511 healthy volunteers (254 males and 257 females) where there was a comparison of African, Asian and Caucasian hair growth patterns. African hair was characterized by both low growth and low hair density, Chinese hair had low density and high growth rate and Caucasian hair was characterized by high density (Loussouarn, G., El Rawadi, C. and Genain, G. (2005), Diversity of hair growth profiles. International Journal of Dermatology, 44: 6–9. doi: 10.1111/j.1365-4632.2005.02800.x) Despite those findings the article does explain that the findings are just too simplistic to draw strong conclusions and does indicate additional investigations should be conducted within each ethnic group.
So the simple answer? Three to six inches per year. But there are
many contributing factors that can lead to more or less growth than
that. Rather than focusing your energy on hair growth, we recommend you
turn your focus to length retention.
Retention is just as important (or more important) than hair growth
Honestly, no matter how fast your hair grows, if you do not learn
proper ways to retain much of that growth, then your hair will not reach
longer lengths. Retention is preserving the hair that grows out of the
scalp and keeping it healthy by keeping it moisturized and gently
handling the hair to reduce breakage; this also includes trimming when necessary.
There is no need to schedule trims unless you are coloring,
straightening, not sealing, and caring for their ends. The ends are the
oldest part of the hair, therefore making them fragile and the most
exposed to damage, especially when wearing the hair loose.
Can you make your hair grow faster?
Biotin has become the go-to for hair growth stimulant, but do many
actually know what it is? “These B complex vitamins (also known as
vitamin H) are important in metabolism, helping your body to process
energy and transporting carbon dioxide from your body’s cells,” says
board-certified dermatologist Dr. Susan Stuart. Biotin
is all the craze for growing healthier hair, nails, and clear skin and
we are seeing a whole new generation of supplement takers for this
beauty benefit, but according to Dermatologist Dr. Richard Scher, it is
not totally clear what role biotin plays.
According to Dr. Scher,
“Biotin deficiency is rare and low levels may result in brittle nails
and hair loss, however, hair loss and brittle nails may have multiple
causes and taking biotin supplements may actually halt this process and
even help to reverse it.” Want another expert opinion? Check out
cosmetic chemist Sister Scientist’s article Biotin and Castor Oil: Do They Really Work? Many of the NaturallyCurly editors have tried biotin, so to read more about how their hair (and skin) reacted, read We Tried Biotin, Here’s What Happened.
Remember that it imperative to eat a healthy diet,
exercise regularly, reduce stress, maintain a clean scalp, and follow
your doctor’s order for a holistic approach to healthy hair. Supplements
can be taken in addition to those things with clearance from your
primary care physician.