Final answer:
A mask that seals the skin and retains moisture usually contains occlusives that form a protective layer, contrasting with humectants that draw moisture but are often paired with occlusives for hydration.
Step-by-step explanation:
The type of mask that seals the skin, locking in moisture, and often giving a firm, taut feeling after removal is one that typically features occlusives. These ingredients form a protective coating on the surface of the skin, effectively preventing moisture from escaping. This action contrasts with another group of substances called humectants, which have the ability to absorb water. Nevertheless, humectants are usually used in combination with occlusives to achieve a moisturizing effect, because humectants alone can draw water from the deeper layers of skin to the surface, potentially making the skin drier. A study in Skin Research and Technology suggested that humectants do not inherently provide a moisturizing effect when used alone.