Which of the following best describes hyaluronic acid?

Hyaluronic acid is indeed best described as a glycosaminoglycan (GAG) that plays a crucial role in hydration within the dermis. It is known for its remarkable ability to hold onto water, which helps maintain skin moisture and overall hydration levels. This property makes hyaluronic acid essential for skin elasticity and volume, contributing to a plump and youthful appearance. Its presence in the dermis aids in maintaining the skin's structure, allowing it to remain supple and resilient.

While options that mention hydrating fluids in the epidermis, structural support, or elastic proteins may touch on related aspects of skin health, they do not accurately encapsulate the specific role and nature of hyaluronic acid. Therefore, recognizing it primarily as a GAG that significantly influences hydration in the dermis highlights its importance in skincare and skin physiology.