Sebum is an oily substance secreted by the sebaceous glands that help keep your skin soft and supple. As you age, however, your skin becomes less able to produce enough sebum to maintain its moisture levels properly. This causes the fat in your skin to dry up along with the collagen (the elasticity of your skin), resulting in thinning skin prone to wrinkles and other aging-related problems like dryness and lack of elasticity.

Replacing what's lost with topical products containing ingredients like natural oils or glycerin is essential. If you don't replace what's lost through proper hydration and daily care, your skin will become dry and lose its elasticity—something we all want to avoid!

Source: American Academy of Dermatology https://www.aad.org/public/diseases/a-z/dry-skin-causes