A combination of factors can cause facial lines. It’s not just about the cellular changes that may occur, or reduction of collagen, or damage caused by free radicals from the sun and the environment.

Repeated muscle contractions from frowning, squinting, or raising eyebrows cause skin to furrow and fold, gradually resulting in the formation of facial lines. BOTOX^® Cosmetic works beneath the surface and temporarily reduces the underlying muscle activity that causes moderate to severe frown lines, crow’s feet and forehead lines in adults – to help them look visibly smoother.

When you frown or concentrate, the muscles between your brows contract, causing your skin to furrow and fold. Your specialist will inject these muscles to help make frown lines temporarily look better.

When you squint or smile, the muscles around your eyes contract, causing crow’s feet. Your specialist will inject these muscles to help make crow’s feet temporarily look better.

When you raise your eyebrows, the muscles on your forehead contract, causing skin to furrow and fold. Your specialist will inject these muscles to help make forehead lines temporarily look better.

SOURCE: https://www.botoxcosmetic.com/what-is-botox-cosmetic/how-botox-cosmetic-works