Final answer:
Conditioners commonly use humectants to absorb moisture and occlusives to form a barrier that prevents moisture loss; they are often used in combination to effectively moisturize the skin or hair.
Step-by-step explanation:
The substances in conditioners that absorb moisture or promote the retention of moisture are known as humectants. These ingredients include materials like glycerin, propylene glycol, and sorbitol, which can draw water from the air or the dermis into the epidermis when humidity is high.
However, they are often combined with occlusives to form a barrier on the skin surface to prevent moisture loss, as humectants alone may not provide an adequate moisturizing effect according to a study published in Skin Research and Technology in 2001.
Occlusives could be ingredients such as petroleum jelly, lanolin, and various oils. Conditioners also contain emollients like silicone, which smooth and soften the hair cuticle, as well as water, emulsifiers, and thickeners that contribute to the product's consistency and application.