Which of the following is NOT a typical external factor influencing skin health?

Genetics is considered an internal factor influencing skin health, rather than an external one. Internal factors refer to aspects that are inherent to an individual, such as their genetic makeup, which can determine skin type, conditions, and overall skin resilience. On the other hand, the other options – climate, sleep, and stress – are external factors. Climate can affect skin hydration and barrier function, sleep plays a crucial role in restorative processes for the skin, and stress can lead to conditions like acne or psoriasis through hormonal changes. Understanding these distinctions helps in assessing factors that can be managed or modified to improve skin health.