INTRODUCTION
The way men are perceived, in general, has changed dramatically in the past fifty years due to changes in society, media, and technology, leading to an increased focus on male appearance and aesthetics, that promote overall health and wellbeing. More than ever, men seem to be held to higher standards of beauty and youthful appearance, which can be influencing factors for a man’s self-confidence, relationships, and career success. This is reflected in the increased interest in men’s skincare products and minimally invasive cosmetic procedures.1,2 As skin plays a major role in aesthetics, men are increasingly aware of the benefits of skincare products that can promote and support healthy and youthful looking skin by reversing and preventing the signs of skin aging such as lines and wrinkles, hyperpigmentation, rough skin texture, and dryness.Due to historical and cultural focus on female beauty and appearance, skincare products have been predominantly developed and tested for women. Physiological differences between male and female skin exist both in skin structure/anatomy as well as in the aging process. Male skin has thicker epidermis and dermis containing more collagen.3,4 Influenced by the gradual decrease of testosterone, male skin thickness gradually decreases with age, unlike female skin which shows a rapid decrease in thickness after menopause. Several studies demonstrated that male skin has greater sebum production, which is also influenced by hormones.5,6 While sebum has important waterproofing and lubricating functions, excess sebum production is associated with enlarged pores in men and can contribute to acne, both of which are common aesthetic skin issues.7 The presence of coarse facial hair further contributes to male skin issues. Shaving is associated with redness, dryness, hyperreactivity, and pseudofolliculitis barbae (ingrown hairs or razor bumps), and the increased microvasculature in male skin, which supports thicker and longer terminal hairs, could contribute to these symptoms.8 Furthermore, anatomical differences in bone structure, musculature, and fat deposition that determine typical male facial features also influence the male aging process.9,10 Detailed overviews of gender differences in skin physiology and aging are provided in several review papers.9,11-13 Lifestyle and behavior play an important role in skin health as it greatly determines the exposure to extrinsic factors contributing to skin damage and aging (such as smoking, pollution, and sun exposure) as well as the adoption of preventative measures to maintain healthy youthful looking skin. For example, men are more likely to smoke and work outdoors.11 Several studies have demonstrated that men are less likely to use sunscreen or other skincare products such as cleanser or moisturizer.10,14,15 Ultraviolet and infrared radiation from sun exposure can degrade the dermal extracellular matrix (collagen, elastic fibers), cause DNA damage, and generate reactive oxygen species (ROS) that can accelerate skin aging.16 ROS and oxidative stress can be particularly damaging in men compared to women, since estrogen upregulates the expression of innate antioxidants, thus increasing the natural antioxidant capacity in women.17
