Medical myth: shaved hair grows back faster and thicker

Hair removal is a modern obsession. Despite the economic downturn, the beauty industry is booming, and it seems that a big part of looking good is getting rid of unwanted hair. Men as well as women are increasingly forking out big dollars for “permanent” hair removal treatments, preferring to shun the traditional character-building cold steel of a safety razor.

Maybe it’s the risk of cuts, but undoubtedly part of the attraction of longer-term hair-removal treatments is the conventional wisdom that shaved hair grows back faster and thicker than it was before.

Some teenage boys hope this one is true, but pretty much everybody else will be relieved to know it’s definitely a myth. For a definitive (and very old) scientific reference this one from 1970 is as good as any since. But it’s fun to speculate about why this belief persists.

The rate of hair growth is determined by a number of factors including genetics, nutrition and nerve function to the area of skin.

When you’re healthy, hair growth is determined by the length of time that the follicle spends in the anagen (growth) phase. Around 80% of the your follicles are in this stage at any time, and they can remain in anagen phase for years at a time. The other phases of the hair growth cycle are the catagen (transitional) phase, which lasts for a few weeks after the anagen ends, and the telogen (dormant) phase.

Head hair grows around 1.25cm a month.NathanaelB

Loss of chunks of hair due to stress, chemotherapy or major surgery occurs when large numbers of follicles hit the telogen phase at the same time, under the influence of regulatory hormones.

Some medications other than chemotherapy drugs can have a similar effect, including beta-blockers such as propranolol for blood pressure, tricyclic antidepressants like amitriptyline and epilepsy drugs such as sodium valproate.

Some medical conditions can cause accelerated hair growth, or a change in the type and distribution of hairs. Excessive exposure to male-type hormones (androgens) will result in more hair on the body and face, and less on the scalp.

The new hair may also be thicker and darker than the previous hair that grew there. This is because androgens cause the hair follicles to produce a specific type of fairly robust hair (androgenic hair), whereas female hormones such as oestrogen stimulate the growth of smaller, lighter hairs known as vellus hair.

Under usual conditions, a person’s hair growth stays at a fairly constant rate: an average of 1.25cm a month for head hair (including ears and nose, gents). Body hair tends to reach a certain length and stop growing, then fall out. The vast majority of body hair is vellus in type.

The perception of faster growth once shaving begins is probably a reflection of increased awareness and possibly even self-consciousness of the area.

There is no convincing evidence I can find that you can improve your genetically and hormonally determined optimal growth rate by taking supplements of any type. Nor can supplements prevent hair loss or improve the appearance of hair. No credible studies have ever been done on the subject, despite a number of product manufacturers making these claims.

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The idea that hairs grow back darker and thicker is also an illusion, created by the fact that hairs tend to taper towards their ends. Shaving them at the base will result in a blunt-ended hair that feels more obvious and is slightly thicker than the end of the hair that has been cut. The base of the hair has been this thickness all along. But compared with the end of a longer hair, it seems a lot thicker.

Plucking and waxing removes the hair from the follicle at the base, meaning it will take a bit longer to regenerate and will come out with a tapered end rather than a blunt one. This is probably why plucking and waxing have a reputation for causing hair to grow back more sparsely.

So hair is hair is hair. It grows, it falls out. Sometimes it gets plucked, waxed or lasered. Like many bodily functions, your hair’s appearance and behaviour will reflect your overall health and your genetic heritage. Unless you have a condition affecting the skin or the regulation of the hair cycle, you can’t make it grow faster or thicker.

Michael Vagg, Clinical Senior Lecturer at Deakin University School of Medicine & Pain Specialist, Barwon Health

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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