Shaving the hair of newborns is a commonly practiced tradition in our country. The widespread belief is that shaving hair off will cause it to grow back darker, coarser and faster. This misconception is often reinforced by popular media sources, and probably by people contemplating the quick appearance of stubble on their own bodies after shaving.
Scientific evidence strongly disproves these claims. As early as 1928, a clinical trial showed that shaving had no effect on hair growth. More recent studies confirm that shaving does not affect the thickness or rate of hair regrowth. In addition, shaving removes the dead portion of hair, not the living section lying below the skin’s surface, so it is unlikely to affect the rate or type of growth. Shaved hair gives the hair a blunt tip. The tip might feel coarse or “stubbly” for a time as it grows out. During this phase, the hair might be more noticeable and perhaps appear darker or thicker — but it’s not.
Similarly, the new hair has not yet been lightened by the sun or other chemical exposures, resulting in an appearance that seems darker than existing hair. Shaving hair doesn’t change its thickness, color or rate of growth.
The rate of hair growth is determined by a number of factors, including genetics, nutrition and nerve functioning of the 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 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.
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.
Other medications can have a similar effect, including beta-blockers such as propranolol for blood pressure, tricyclic antidepressants like amitriptyline and epilepsy drugs like sodium valproate.