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The Science of Hair Growth and Skin

The Relationship Between Skin and Hair
Contrary to popular belief, hair itself is not alive. In fact, the only living portion of the hair structure is the hair root (or papilla), which is found at the base of the hair follicle deep within the skin. A strand of human hairs consists of three parts—the cortex, the cuticle and the medulla.

The safest and most effective hair removal treatment options begin with an understanding of how to treat skin and hair on different parts of the body.

In general, the skin on a woman’s legs is taut and smooth, but because there are few oil-producing glands located there, the skin can become relatively dry. Hydrating hair with warm water causes it to swell and can make it up to 60 percent easier to cut.

The hair in the bikini area tends to be more coarse and curly than hair on the legs or underarms. This area is particularly sensitive and is also less taut than skin on the legs, providing more resistance for the razor. Since skin in the bikini area is particularly sensitive, always soften the hair in warm water before you shave and use light strokes. To help further soften hair and to ensure razor glide on ultra-sensitive skin, be sure to use a moisture-rich shave gel.

Underarm hair is generally thicker, denser and grows slightly faster compared to other areas. The skin also tends to be less taut than on the legs. Compared to other areas of the body, the number of glands in the underarm area leaves skin relatively moist.

Unwanted facial hair often appears on the upper lip, chin and sides of the face. In women, facial hair may range from normal levels (fine, medium or coarse) to abnormal excessive hair growth, arising from underlying clinical conditions.

On average, hair grows about 0.2-0.3 mm per day. This rate is biologically fixed and isn’t influenced by our diet. Only targeted pharmaceuticals can have an effect on hair re-growth. Between starting to grow and falling out, each hair passes through three distinct stages:

  • Anagen—the growing phase
  • Catagen—the intermediate phase
  • Telogen—the shedding phase

The hair follicle lies a comparatively long way down below the skin’s surface: its growth cycle to reach and break through the skin’s surface takes about two to four weeks, which can explain the much slower re-growth time women experience with root hair removal techniques. When talking about a surface hair removal method such as shaving, this is why women can feel a slight roughness after one to two days as the hair returns.

What Are the Effects of Shaving?
The effects of shaving on human hair have been studied extensively by P&G Beauty & Grooming scientists. Contrary to conventional thought, the scientific conclusion is that shaving does not increase the re-growth of shaved hair, nor does it alter the size or color of the hair. Further, shaving doesn’t cause shaved hair to grow back thicker, darker or faster.

Shaving does alter the tip shape of the re-growing hair, which may initially change the way hair feels to the touch when it grows back. For the closest, smoothest shave, it is recommended you shave against the direction of hair growth. However, this depends on your own personal preference and the sensitivity of the skin.

Seasonal Cycles
P&G Beauty & Grooming scientists have long studied the seasonal impact on hair and skin. While some believe there is a springtime growth spurt in hair, others tend to think hair is more hormonally driven. For example, in pregnancy, many women find their hair thicker even though they are not growing more hair. This can be explained by the higher levels of estrogen increase the growing stage of hair, leaving fewer hairs in the resting stage. Hairs are shed more slowly, creating the impression of increased thickness.

Women vs. Men
Men’s and women’s shaving needs differ in a number of ways. Men typically shave their faces and necks, whereas women shave their legs, underarms and bikini area. Women’s total shaving area is 18 times greater than men’s total shaving area—676 square inches for women vs. 38 square inches for men.  

Hair Growth
Much like men’s facial hair, women’s underarm hair tends to grow in different directions. Women’s leg hair tends to grow in one direction, down, while the hair around the bikini area tends to grow in towards the center and down. The growth rate for underarm hair is approximately 50 percent greater than that of leg hair. However, men’s beards grow fastest. 

hair growth direction

Shaving Regimens
Women are faced with having to shave hard-to-reach places, which they are unable to clearly see or easily reach. The majority of women also shave in the shower or bath: a relatively wet, slippery and not always well-lit environment. Men, for the most part, tend to shave at the bathroom sink.

True or False:
Women and men can share the same razor.
False: Sharing a razor is not hygienic, and a man’s razor has been designed for men and not for women. When shaving, women should use a razor which has been designed for the unique contours and topography of a woman’s body as well as the way that they shave.

Women can use the same shaving gel that men use on their faces.
True: Women can use shaving gel that men use on their faces. However, since women’s legs tend to be drier than a man’s face, you will get better results from using a moisture-rich shave gel designed for women.

 Additional P&G Beauty & Grooming Resources:


Claire Girdler headshot

“Women and men have unique shaving needs, so it’s important to choose a razor that fits best with your preferences. If women use men’s razors, for example, they will not get the closest shave possible because it is not designed for the unique contours and topography of a woman’s body.”
Claire Girdler

Sian Morris headshot

 “Women should remember to use razors designed specifically for them to ensure the best and closest shave. Women require razors designed for the many grips used when shaving different body parts as well as good control and lubrication for a less irritating shave. Women’s razors typically have oval-shaped cartridges to fit in all those hard-to-shave areas.”
- Sian Morris



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