Gender difference issues are some of the most basic when considering cosmetic formulation. Male skin is visually much different than female skin and has a unique response to aging and adverse product reactions. When discussing female versus male skin, we shall be talking about fully mature individuals. The unique skin care needs of children will be discussed later.
Probably the most important difference between male and female skin is the skin thickness. Male skin is thicker than female skin, in part due to the presence of terminal hair follicles over much of the body. This difference is most pronounced on the face where women have only vellus hairs while men have fully developed terminal hairs taking up space within the skin. The presence of male facial hair is partially responsible for the more favorable appearance of mature men over mature women. As UV radiation activates collagenase to destroy dermal collagen, the male beard allows the skin to resist wrinkling, which is not the case in females. Thus, photoaged males do not exhibit the pronounced redundant facial skin seen in photoaged females. The thicker male skin is also better at diffusing UV radiation, especially in the UVA range, which penetrates more deeply causing greater damage in female skin. The media that tends to prefer images of younger women and older men further magnifies the gender differences in photoaging.
Differences in skin thickness also impact the frequency of adverse product reactions suffered by the two sexes. Women experience adverse reactions more commonly than men. The thinner skin may allow irritants and allergens to penetrate deeper in female skin, but the increased incidence may also be due to greater product usage. Women overall use more skin care products and cosmetics than men. This increased usage magnifies the chances of contacting an irritant or an allergen. Women are also more likely to undergo procedures that destroy the skin barrier, such as facial peels, microdermabrasion, spa treatments, etc. Furthermore, women are more likely to engage in anti-aging topical products that can create barrier damage, such as topical tretinoin, glycolic acid, lactic acid, etc. This damage to the stratum corneum further increases the chance for magnification of a mild adverse reaction into a more major problem. This artificially created increase in adverse reactions experienced by women has been termed “polypharmacy” by some who wish to impart the concept of overusage of prescription and over-the-counter products by youth-seeking women. Others use the term “iatrogenic sensitive skin” to emphasize the skin sensitivity created by exaggerated product use.
Perhaps one of the most important differences between male and female skin is the relative balance between male testosterone and female estrogen and progesterone. Male and female skin is quite similar up until puberty, at which time sexual differences become more pronounced. Both testosterone and estrogen cause the production of facial and body sebum. This onset of oil production sets the stage for acne whereby the (Propionibacterium acnes) bacteria now has a food supply to encourage abundant growth. More sebum production is triggered by testosterone accounting for the generally greater severity of acne in males over females. However, females with higher than normal testosterone production, due to hormonal abnormalities, such as polycystic ovary disease, may experience acne equally severe to any male. The onset of hormones also triggers an increase in apocrine sweat, the scented type of sweat that is produced by specialized sweat glands on the eyelids, breasts, scalp, buttocks, and in the armpits. Both sebum and apocrine sweat create different skin cleansing needs and alter the skin biofilm in ways that can dramatically affect cosmetics and skin care products. The formulator must consider the substances on top of the skin.