Injectable Cosmetic Procedures for the Male Patient

a flatter, more angular appearance.⁹ Distortion of these proportions can result in feminization of the face.¹⁰ Conversely, dramatization of these masculine features can also have a negative effect. Exaggerated features such as an excessively broad chin, heavy brow, or wide face may be perceived as aggressive or threatening.11

Overall, men have a greater muscle mass than women due to anabolic effects of androgens on skeletal muscle, and this holds true for the male face.^{12, 13} Furthermore, men experience a greater amount of facial muscle movement even after accounting for differences in facial size.¹⁴ Taken together, the greater muscle mass and amount of facial muscle movement may help explain why men have deeper, more pronounced rhytids with a unique distribution. This difference in muscle mass is an important consideration when treating the male patient with injectable neurotoxin.

Men have a thicker epidermis and dermis than women and the subcutaneous adipose layer is less prominent.^{15, 16} The increased skin thickness and collagen content is attributed to the androgen receptor pathway, and may explain why male skin thins steadily with age while the thickness of female skin is relatively constant until menopause.¹⁷ Male facial skin has an increased vascularity, making men more prone to bruising after minimally-invasive cosmetic procedures and injections.¹⁸

Men experience a gradual, steady decrease in total and free testosterone as they age²⁰ resulting in a consistent decline in soft tissue thickness, whereas women have an abrupt loss around the fifth decade, corresponding to the time of menopause.²¹ In general, as men age they have more severe rhytids than women with the exception of the perioral area.^{22, 23} This is thought to be the result of the thinner subcutaneous adipose layer in combination with thicker skin and more prominent

facial musculature.⁹ The aging male also experiences more prominent volume loss in certain anatomic locations. For example, men experience a greater downward shift of the lower eyelids with age.²⁴

The male face ages differently due to particular behaviors that affect the skin. Relative to women, men experience increased UV radiation exposure from outdoor occupations and lower adherence to sun protection behaviors.²⁵ Additionally, the increased prevalence of smoking contributes to advanced skin aging in men.^{26, 27} Men are poor consumers of cosmetics including sunscreens.²⁸ Men are less likely to see a dermatologist or perform a self-skin exam. All of these factors contribute to more severe rhytid formation, loss of elasticity, and pigmentary alterations seen in the aging male patient.

Given the greater width, height, and muscle mass of the frontalis, injection of botulinum toxin in the forehead of men to decrease horizontal rhytids requires a greater number of injection points and units.⁵ Two studies have shown differences in efficacy in males. Kearney et al. found abobotulinumtoxinA to be less effective in men at similar doses when compared to women.²⁹ When treating the glabella, Carruthers et al. concluded that increasing doses of onabotulinumtoxinA correlated with decreased ability to frown, improved global assessment, and increased feelings of satisfaction, self-confidence, and attractiveness.³⁰ Although men require greater units of neurotoxin, the goals of the patient must be kept in mind. Rhytids on the male face can produce a distinguished and “wise” look. Therefore, a natural aesthetic with some movement of the frontalis is advocated for most patients.

An important distinction to consider when injecting neuromodulator to the male forehead is the presence of androgenetic alopecia. Extending the injections to the frontal scalp can prevent unnatural wrinkling in the alopecic skin, which otherwise would provide a sharp cutoff (Figure 1).

The male eyebrow sits lower on the orbital rim, and lies more horizontally and straighter than in women.^{6, 7} Arching of the eyebrow can give a feminine look. Conversely, a brow that