Many people say, "If you shave your hair, it will grow back thicker." But this is not true. A scientist tested it in 1928, and shaving did not change the hair.

Hair is made deep under the skin, and a razor only cuts the top part. New hair looks darker because it is cut at its thickest point. Also, many people start shaving when their body hair is naturally getting darker.

It is widely believed that shaving makes hair grow back thicker and darker. However, this idea was tested long ago. In 1928, the American anatomist Mildred Trotter studied people who shaved their legs for several months. Shaving did not make the hair thicker, darker, or faster-growing.

A 1970 study, in which young men shaved only one leg, found the same result. The reason is simple. Hair is produced in the hair follicle under the skin, and a razor only cuts the part above the surface.

So why does it seem thicker? Natural hair becomes thinner toward the tip, but shaving cuts it at its widest part, leaving a blunt end that feels rough. In addition, people often begin shaving during puberty, when hormones naturally make body hair darker.

Teenagers picking up a razor for the first time are often warned that shaved hair grows back thicker, and the stubble that follows seems to prove it. The claim was tested almost a century ago. In 1928, the American anatomist Mildred Trotter reported that months of regular shaving did not increase the thickness, color or growth rate of hair. A 1970 study used a neat design.

Researchers shaved only one leg of each young male participant and left the other as a comparison, and again no difference appeared. Both studies were small, but their results fit what is known about hair biology. A hair's diameter, pigment and growth rate are set by the follicle beneath the skin, which a razor never touches.

So where does the illusion come from? An uncut hair tapers to a fine point. A razor slices it near its widest part, leaving a blunt tip that looks darker and feels coarse.

New hair has also not yet been lightened by sunlight. Perhaps most important of all, people usually start shaving during puberty, exactly when hormones are making body hair denser and darker. Two things that happen together are easily mistaken for cause and effect.