Introduction
The skin, in addition to being an admirable union of cells, tissues and appendages, an interface between our body and the external environment, is an organ that strongly expresses gender differences, both from the physiological and structural point of view, mainly due to the different hormonal and genetic structure and behavioral factors.
Differences from female skin
The skin has the same basic structure and the same composition in men and women, but shows physiological differences, basically due to the different hormonal structure.
Role of Testosterone
Men have greater secretion of steroid hormones than women. In particular, among androgens, the most important hormone is testosterone, responsible for many differences in the physiological characteristics of the two genera. Testosterone determines the extent of skin thickness, sebaceous secretions and hair follicle activity. The influence of the hormonal factor on the thickness of the skin has been shown by administering estrogens to post-menopausal women: after 12 months of therapy it was found that the dermis increases in thickness and that the epidermis is less atrophic. therefore, due to the greater presence of testosterone, man has a greater thickness, on average 20%, compared to the female one, and a greater richness of fibers, thus resulting in a much more dense and resistant, both at the level of the epidermis and of the stratum corneum, both at the level of the dermis, characterized by a greater density of collagen fibers. However, the thickness of the man's skin progressively reduces with advancing age, while that of the woman's skin remains more stable until the age of menopause, and then decreases dramatically.
The greater resistance of man's skin is the reason why, with the same aggression against external agents, he more slowly undergoes chromatic variations, sagging skin, loss of tone etc. compared to the female one. It follows that the signs of aging appear on the male face at a later age than the woman, but, once they have appeared, the wrinkles quickly become deep and very evident.
If the skin of the man is thicker and less soft than that of the woman, in all the phases of life, the adipose tissue is more represented in the woman. Also due to the action of testosterone, which stimulates sebum production up to twice that of women, male skin is more oily and the pilo-sebaceous follicles are more dilated. As a consequence, it is possible to observe a higher lipid content in humans, therefore a greater predisposition to skin impurities, folliculitis and acne. The average values of sebum secretion are significantly higher in men than in women in the age range between 20 and 69 years, but not between 15 and 19 2.
After the age of 50, sebum secretion in humans tends to stabilize, while in women it decreases, probably due to decreased ovarian activity.
Through clinical evaluations and instrumental bioengineering methods, other differences in the biophysical properties of the skin were verified, such as hydration or the degree of skin desquamation, measured using the D-Squames technique, plastic disks covered with adhesive material used to perform the sampling of corneocytes, which are then analyzed with various methods, for example evaluating light transmission through the disk, weighing the disk before and after its application, or using colorimetric techniques.
In both tests no differences were observed between the two sexes 3.
According to one study, even the measurement of TEWL (transepidermal water loss), or the amount of water that is lost from the dermal and epidermal tissues to the external environment through the stratum corneum, does not differ between men and women in any period of life 4. Another study, on the other hand, found lower TEWL values in women 5. Skin elasticity, assessed with a cutometer, an instrument that measures the vertical deformation of the skin surface when it is sucked by a measuring probe, does not differ between the two sexes 6.
The extensibility of the skin is identical in men and women but, after having hydrated it, it increases only in women and this is a consequence of the lower thickness of the dermis in women compared to men 7.
The incidence of irritative dermatitis is greater in women than in men but, since some studies have shown similar values of TEWL in the two sexes after irritation with sodium lauryl sulfate, it can be deduced that the dermatitis that afflicts women is occupational.
Scientific evidence indicates that the composition of sphingolipids in the stratum corneum varies significantly over the course of life in women but not in men, due to the influence of female hormones. In particular, in the period preceding puberty up to adolescence there is a significant increase in ceramides 1 and 2, simultaneously with a decrease in ceramides 3 and 6. After maturity, there is a reduction in ceramide 2 and an increase of ceramide 3 8. These lipids play an important role in ensuring the proper functioning of the skin's hydrolipid barrier.
Differences were also found between men and women in the metal content in hair (larger amounts in women). There are no changes in the copper content of the skin in men, while an increase in age has been observed in women 9.
Skin colour
The male skin, compared to the female one, shows a more dull complexion, due to a lower cellular renewal, and darker, due both to hormonal factors, and to the differences in the content of melanin, hemoglobin and carotene.
Generally, in both sexes, the complexion becomes darker with age, but it is possible to observe more complex variations: from the end of childhood to the beginning of puberty there is a progressive browning in both sexes 10; during adolescence the skin of both lightens, but to a greater extent in women. Simple hormonal effects cannot explain this difference, since both estrogens and testosterone tend to cause a browning of the skin rather than a clearing.
The chromatic variation could therefore be partially attributed to the different habits of exposure to sunlight by the two sexes. In one study it was shown that the color of the skin of the forehead of a group of adolescents was darker in boys than in girls. The pigmentation of the upper arm, however, less exposed to light, varied in the different stages of adolescence. Girls were darker than boys in early adolescence; during the middle adolescence the pigmentation was similar in the two sexes; during late adolescence girls were significantly lighter than boys.
Acidity of the Skin
Another fundamental difference in the two genders is the acidity of the skin, higher than that of man with a pH value of 4.5 compared to 5.8 for women. The higher acidity values, characteristic of human skin and due to the greater presence of lactic acid, preserve it more from bacterial infections, but make it more irritable.
Peli and Barba
Another characteristic of male skin is the presence of a highly developed hair system. In particular, the beard is made up of about 15, 000 hairs with an average growth of 13.7 centimeters per year. Shaving is an aggressive operation as it involves a repeated removal of part of the hydro-lipid film and the superficial layers of the epidermis, causing alterations in its equilibrium with the appearance of phenomena to the skin, if poorly performed or performed with unsuitable cosmetic instruments and products. such as irritation, dryness, micro-cuts, impurities and small infections.
Finally, because testosterone generally inhibits the immune system through complex mechanisms, while estrogen stimulates it, men's skin has - at least in this respect - a greater predisposition to viral and bacterial infections and their resolution is slower.
1 Maheux R, Naud F, Rioux M, et al. A randomized, double-blind, placebo-controlled study on the effect of conjugated estrogens on skin thickness. Am J Obstet Gynecol 1994; 170: 64243. Shuster S, Black MM, McVitie
2 Few PE, Strauss JS. Endocrinologic control of the development and activity of the human sebaceous gland. J Invest Dermatol 1974; 62: 191-201.
3 Jemec GBE, Serup J. Scaling, dry skin and gender. Acta Derm Venereol (Stockh) 1!) 92; Suppl.l77: 26-8.
4 Cua AB, Wilhelm KP, Maibach HI. Frictional properties of human skin: relation to age, sex and anatomical region, stratum corneum hydration and transepidermal water loss. Br J Dermatol 1990; 1:! 3: 473-9.
5 Goh CL, Chia SE. Skin irritability to sodium lauryl sulphate - as measured by skin water vapor loss-by sex and race. Clin Exp Dermatol 1988; 13: 16-18.
6 Cua AB, Wilhelm KP, Maibach HI. Elastic properties of human skin: relation to a, ge, sex and anatomical region. Arch Dermatol Res 1990; 282: 283-8.
7 Auriol F, Vaillant L, Machet L, et al. Effects of short time hydration on skin extensibility. Acta Derm Venereol (Stockh) 1993; 73: 34 & 7. Yamamoto A, Serizawa
8 Denda M, Koyama J, Hori J, et al. Age and sex-dependent change in stratum corneum sphingolipids. Arch Dermatol Res 1993; 285: 415-7.
9 Sturado A, Parvoli G, Doretti L, et al. The influence of color, age and sex on the content of zinc, copper, nickel, manganese, and lead in human hair. Biol Trace Elem Res 1994; 40: 1-8.
10 Banerjce S. Pigmentary fluctuation and hormonal changes. J Genet Hum 1984; 32: 345-9.
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