Which ingredient category in moisturizers is defined as water-binding agents?

• A. Emollients
• B. Occlusives
• C. Surfactants
• D. Humectants

Answer: (D)

Humectants are water-binding agents. They attract and hold water, helping to add and retain moisture in the outer layer of the skin. In a moisturizer, humectants pull water from the environment (or from deeper skin layers if humidity is low) into the stratum corneum, increasing hydration and making the skin feel plumper and more moisturized. Common humectants include glycerin, propylene glycol, sorbitol, hyaluronic acid, and urea.

This is different from emollients, which primarily soften and smooth the skin by filling in spaces between skin cells; occlusives, which form a barrier on the skin to prevent water loss; and surfactants, which reduce surface tension to help cleansing or emulsification rather than hydration. Humectants play the key role of attracting and binding water to improve skin moisture content.