What is the primary function of sebum?

The primary function of sebum is to provide lubrication and waterproofing to the skin and hair. Sebum is an oily substance produced by the sebaceous glands in the skin, and it plays a crucial role in maintaining skin hydration by preventing moisture loss. This oily layer helps to keep the skin supple and prevents it from becoming dry and cracked.

Additionally, the waterproofing properties of sebum ensure that the skin remains protected against external factors, such as water and environmental pollutants. This barrier function is essential for overall skin health, as it helps to maintain the integrity of the skin's surface and supports its ability to act as a protective barrier against various external elements. Thus, the correct answer highlights sebum's key roles in lubrication and waterproofing within the context of skin health and function.