Why Does My Hair Grow So Fast? The Causes of Fast Growing Hair


My hair has always grown so much faster than the hair of my friends. It was nice when I was trying to grow out my hair, but can be annoying when I have a shorter style that I like and have to go to the salon frequently just to maintain it. This frustration led me to finally research why hair grows so fast in some people but not others.

So why does my hair grow so fast?Hair growth rate varies widely among people. DNA largely determines a person’s hair growth rate. However, it is dependent on many factors including the part of the body, ethnicity, gender, age, stress level, and state of health.

I dove deep into the research and found some surprising things that explain a lot about my hair experiences. Read on to learn who is most likely to have the fastest growing hair.

How Fast Does Hair Grow on Average?

Before you learn why your hair is growing so fast, you may want to know exactly what is normal for human hair growth.

Scalp hair grows at a rate of about 0.6–1.4 cm (.03-.56 in) per month in general. However, hair growing as fast as 3.36 cm/month (1.3 in/month) has also been noted in research.

Here is the average growth rate of hairs on different parts of the body, according to data found in a research paper by Pragst F. Balikova, MA.

Part of BodyAverage Growth Rate (mm per day)
Scalp, non-bald 0.32–0.46
Scalp, alopecia0.08–0.15
Beard0.25–0.29
Underarm0.29–0.33
Pubic Area0.3
Eyebrow0.15–0.16
Thigh0.13–0.25
Trunk/Arms/Legs0.27
Forehead0.03

Body Hair Growth Rate

If you are wondering about why your body or facial hair is growing so fast, the reason is most likely due to hormones.

Hormones affect hair growth in many ways, including the growth rate. If we are talking about body and facial hair, testosterone often increases the rate of growth and estrogen often decreases it.

This is why women with a lot of facial and body hair often have higher levels of testosterone than other women. Not only does testosterone make hair grow in these places, it makes the hair grow faster.

In addition, substances such as minoxidil, cyclosporin, diazoxide, and
chromakalin can increase the growth rate of body and facial hair.

Scalp Hair Growth Rate

If you are wondering why your scalp hair is growing so fast, then the main reason is likely ethnicity or hair thickness. But other factors may be at play too.

Ethnicity

Hair growth rates vary significantly between ethnicities.

In a large study on the diversity of human hair growth, people of African descent tended to have hair that grew the slowest as well as the thinnest hairs.

People of Asian descent had hair that tended to grow the fastest along with the thickest hairs.

And people with European descent fell in the middle.

Here’s a chart from that study showing the diversity in hair growth speeds.

However, as I cover in the next section, this may be more about hair thickness than ethnicity.

Hair Thickness

In a study of Asian and Caucasian subjects with straight and semi-straight hair, thicker hair fibers corresponded to a faster growth rate. Thin hair fibers had slow growth rates. This finding appeared to be unrelated to ethnic origin.

Another study analyzed 59,765 hairs and found that thin hairs grew slower than thick hairs.

This may explain why Asian people tend to have hair that grows the fastest. They also have the thickest hairs.

If you have thick hair, that explains why your hair is growing so fast. However, just because your hair seems thick doesn’t necessarily mean that it is actually is thick.

Especially if you are of European descent, you may just have dense hair. That means you have more hair follicles spaced close together and a lot of hairs, but they aren’t necessarily thick.

You can tell if your hair is thick by pinching an individual hair between your fingers and feeling it. If you feel nothing between your fingers, you don’t have thick hair.

If instead, your hair feels like some heavy sewing thread, you have thick hair.

Gender

One study of young adults found that the hair growth rate of scalp hair was pretty similar between males and females. However, hair tends to grow significantly slower at the nape in men.

In contrast, another study of Caucasian subjects found that women without pattern hair loss had a faster hair growth rate than men without pattern hair loss.

Overall, it seems that women are probably more likely to have fast-growing hair, but there will be exceptions to this rule.

Age

Hair growth speed can slow with age. Researchers have found that people under 25 have the fastest growth rates.

In other studies, the average growth rate in prepubescent, adolescent, adult, and older adults have been reported at 0.41, 0.30, 0.34, and 0.32 mm/day, respectively.

So very young people tend to have faster-growing hair, but once you reach adulthood, it tends to stay at the same rate.

However, aging can make hairs thinner over time. And as we have learned, thin hairs tend to grow slower.

Environmental Factors

Environmental factors may affect the growth rate of hair, but their influence is very minimal compared to genetics. Your sex and ethnicity are far more important.

In brief, different living conditions in people of the same origins appear to have a very low influence upon their inherent hair growth parameters. 

-Diversity in human hair growth, diameter, colour and shape. An in vivo study on young adults from 24 different ethnic groups observed in the five continents

Stress

Stress is one environmental factor that may impact hair growth rate by causing hair growth inhibition.

In fact, according to Erling Thom, a Dermatology researcher, many stress-related substances can stop hair growth.

Studies have demostrated that certain stress-mediating substances such as substance P, adrenocorticotropic hormone, prolactin, and cortisol actually inhibit the growth of hair.

-Erling Thom

In addition, severe illness may interfere with hair growth.

The good news about having hair that is growing fast is that you are more likely to be a healthy person!

Final Takeaways

If you have fast-growing hair, the main reason is your DNA and hair thickness. Several other things, like environmental factors, age, stress, and medications may have an impact, but your DNA mostly calls the shots in this department.

Related Questions

Why does my hair grow so fast after waxing?

The most likely reason is that the hairs are breaking and not being pulled out by the root. So instead of taking a week or more to show back up, they are growing back in a few days, just like you shaved.

To ensure this doesn’t happen, make sure you aren’t waiting too long to wax. Longer hairs are more likely to break.

Want to remember this? Pin this to your favorite Pinterest board so you can find it later!

References

Agency for Toxic Substances and Disease Registry: Hair Analysis Panel Discussion: Exploring the State of the Science

Clinica Chimica Acta: State of the Art in Hair Analysis for Detection of Drug and Alcohol Abuse

European Journal of Dermatology: Diversity in human hair growth, diameter, color and shape. An in vivo study on young adults from 24 different ethnic groups in the five continents

International Journal of Cosmetic Science: Relationships Between Hair Growth Rate and Morphological Parameters of Human Straight Hair: a Same Law Above Ethnical Origins?

The Journal of Clinical Endocrinology & Metabolism: Effects of Sex Steroid Deprivation/Administration on Hair Growth and Skin Sebum Production in Transsexual Males and Females

Journal of Drugs in Dermatology: Stress and the Hair Growth Cycle: Cortisol-Induced Hair Growth Disruption

Skin Research and Technology: Gender Differences in Scalp Hair Growth Rates are Maintained but Reduced in Pattern Hair Loss Compared to Controls

Heather McClure

I've been a freelance writer for over a decade, specializing in the spa, wellness, and beauty niches. I've also worked professionally for years in a brick and mortar business in the spa industry. I geek out on researching wellness and beauty topics and love sharing this knowledge with other women.

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