A woman's skin is around 25% thinner than a man's. This is down to the amount of testosterone men have, resulting in thicker, tougher skin with more natural collagen. As women age, their natural production of sebum gradually declines, resulting in drier skin. Another contributing factor is the surface pH of women's skin, which is more acidic than men’s and thus further increases the likelihood of suffering from dry skin in later life. This is why a lot of anti-aging products for older women include more intensely hydrating and nourishing ingredients, since they help to replenish any lost moisture, and therefore actively provide protection for the skin’s barrier.