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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

Medical Myths Medical Myths

The Hair-Raising Myth About Shaving

January 06, 2015

By Robert H. Shmerling M.D.

Beth Israel Deaconess Medical Center

When I was a teenager, my friends told me I should put off shaving as long as possible because shaving makes your hair grow back faster, thicker and darker. So the sooner I started shaving, the sooner I'd have to shave every day. They were right. Before long I was shaving daily and if I skipped, it showed. Of course, over the course of a year or two, that was true of all my friends.

So, is it true that shaving makes your beard grow faster? Is it true that girls should delay shaving their legs as well? Does shaving affect hair growth? If not, why do people believe this myth?

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How Hair Grows

First, let's talk about hair growth. The real action happens below the skin's surface, in the hair follicles. A hair follicle is a specialized gland just beneath the skin where a shaft of hair is produced. The color, length and consistency of a hair are determined in the hair follicle. The number of hair follicles determines the number of hairs over a given patch of skin, which is a key determinant of hair thickness.

There's nothing you can do by cutting a hair shaft at the surface of the skin that will alter how quickly it grows back. You also can't alter its color or texture. And certainly shaving doesn't increase the number of hair follicles, which is the only way to increase hair thickness. That's true whether the hair is located on the face or the legs. The only thing shaving does is shorten hair.

So my friends were wrong: shaving doesn't make hair grow back faster, thicker or darker. They were simply repeating what they'd heard from friends or family who had equally unreliable sources.

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Origins of a Myth

It's easy to assume that when one event follows another, the first one caused the second one. But that may be faulty reasoning. People start to shave when hair becomes noticeable in places they'd rather not have hair. We shave because hair is growing darker, thicker or faster. Shaving does not make that happen.

This myth may also follow from the practice of pruning plants and trees, which is intended to stimulate the growth of new branches. Hair, however, grows strand by strand, from a single hair follicle, without branching.

Another reason for this myth is that stubble — shaved hair that is just starting to grow back — is sharper and more noticeable, and may feel thicker, than hair that's grown out for a while.

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What Really Calls the Hair Shots

If you've ever wondered why hair stops growing (for example, when men become bald) or why it turns gray, it's due to changes in the hair follicle. Hair follicles are influenced by the genes you inherit from your parents, your hormones, and your age. Hair follicles may be programmed to quit making hair or to stop producing pigment. Hair changes over time, whether we like it or not. Your hair will grow until it stops, turn gray when it's ready and fall out on its own schedule.

If thinning hair is the problem, the only highly reliable way to increase the thickness of your hair is to add hair follicles. That's what cosmetic surgeons do: they transplant hair from where it's growing normally to bald or thinning areas.

Other treatments are less reliable but may be effective for certain types of hair loss. For example, minoxidil (Rogaine), applied to the scalp, may improve the health of hair follicles by opening up blood vessels around them. It can be used by men or women. Finasteride (Propecia) delays the death of hair follicles by blocking dihydrotestosterone (DHT), an enzyme related to testosterone. Finasteride is approved only for men with male-pattern baldness.

Sometimes, hair changes are due to more than just getting older:

    • An underactive thyroid can make hair coarse or dry and vitamin B12 deficiency may accelerate the graying of hair.
    • Cosmetic treatments, such as perms, ironing, or coloring can damage hair and unintentionally change its color or appearance.
    • The chemicals used to kill algae in a swimming pool or the copper in the water or pipes are thought to make light- colored hair temporarily turn green.
    • Pregnancy can alter the growth cycles of your hair follicles, temporarily causing a reduction in hair loss that may make your hair seem thicker. Then, after you give birth, an alarming loss of hair may follow. While it's perfectly normal to lose this hair, noticeable thinning or baldness doesn't commonly occur after a routine pregnancy.

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The Bottom Line

You may want to delay shaving simply because there's a lifetime of shaving ahead of you once you start. But delaying your first shave (or any other shave) will not change how your hair grows or how soon you have to do it again.

So shave as often or as rarely as you like. But once it grows back, don't blame its appearance on when you started shaving. It just doesn't work that way.

Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

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