Does shaving cause hair to grow faster, coarser and darker? This age-old question is still asked repeatedly. A quick anatomy lesson on the structure of a hair follicle should help.
The hair follicle and its hair are fundamentally one structure. This structure can be divided anatomically into three segments:
(1) Infundibulum - the upper, funnel-shaped indentation that extends from the polar orifice in the epidermis (the little hole where we aim our needle) to the entrance of the sebaceous gland.
(2) Isthmus - the short midsection of the follicle, bounded by the sebaceous gland duct and the arrector pili muscle.
(3) Inferior - extending from the arrector muscle to the base of the follicle. The expanded lower end of the follicle is the hair bulb, which encloses the oval-shaped vascular-connective tissue papilla. This is an upgrowth of the dermis containing the blood supply
and nerve endings to nourish the follicle.
An anatomic change occurs at the isthmus. The entire follicle beneath the isthmus, can be considered "temporary" because it disappears during the involutional stage, or stage of regression of the hair follicle cycle, and reforms again during the growth cycle. The upper segments, isthmus and infundibular, are "permanent." At the isthmus, the cells of
the inner root sheath disintegrate, and the outer root sheath -- which is no longer in contact with an inner root sheath -- begins to cornify, and form the hair we aim to remove.
The hair shaft (this is the hair that is cut off when shaving) is a dead, cornified structure that extends from the follicle above the surface of the skin: only the follicle is alive. To make any difference in hair growth, the follicle itself must be disturbed. Shaving or cutting the dead structure (hair) will not have any effect on the follicle itself.
Shaving hair is really a form of cutting hair (how many of us tell patient's it is OK to cut with scissors?), done with a razor that cuts off the hair close to the skin. And, like cutting with scissors, shaving has no effect on hair growth. This myth was exploded by Dr. Mildred Trotter at the Washington University School of Medicine.
Under Dr. Trotter's observation, three girls shaved their legs from knee to ankle, twice a week for a period of eight months. At the end of this time, microscopic examination revealed that there was absolutely no increase in the diameter or color of the hairs before or after the shaving period.
After shaving there is an illusion of growth -- which has given rise to the false impression that shaving really does affect the growth. Let us examine those points that appear to support the idea.
1. The shortness of the shaft of a shaved hair allows changes in its length to be noticed more easily. If a hair is shaved right to the skin, and then allowed to grow 1/16", we readily notice the difference. However, if the hair was already 6" long and it grew an extra 1/16" (in the same period as the shaved hair), no one would be able to tell without some accurate way of measuring. Taking the example of the male with a full beard, it is impossible to detect the daily increase in beard growth. But it is a different story with the clean shaven person and his "five o'clock shadow," whose bristle growth can be seen on the very same day.
2. Because the follicles of terminal hair are not at right angles to the skin, shaving exposes more actual area of hair to the eye. If scissors are used to clip a hair, the cut is usually at a right angle to the direction of growth. But shaving -- given the angle of hair to blade -- leaves a longangled cut at the end of each remaining hair fiber. When the hairs grow out from the skin, they keep their "thickened" appearance, especially as they are being compared with the white background of skin.
3. Apparent coarseness is caused by the short, shaved hairs being held more erect by the follicles clasped firmly around them. Hairs do vary in structure, length, rate of growth, and response to various stimuli. But the follicle must be effected, not the hair shaft itself. For instance, sex hormones do not directly govern the development of eyelashes and eyebrows, yet body, axillary, pubic, and facial hairs are directly dependent upon hormonal stimulation for their adult characteristics. These latter hairs are part of the ensemble composing the secondary sexual characteristics. The follicles themselves must be stimulated to cause an increase in hair growth.
Shaving every day, even with vigor, would not effect the deep growing follicle. The increased hair growth you notice on your patients who shave, is in all probability caused by an increased hormonal stimulation. Which would have happened, shaving or no.