Tonya Mckay of Naturallycurly writes;
We hear a lot about the humectants. But many of us may not know what they are and how they work.
Humectants are used in skin and hair-care products to promote moisture retention. These hygroscopic compounds posses a chemical structure that attracts water from the atmosphere and binds it to various sites along the molecule.
There are many different types of molecules that are effective humectants, but the chemical similarity they share is having multiple alcohol (hydroxyl) or similarly hydrophilic sites (such as ethers or ammonium groups) available for hydrogen bonding with water molecules. The strength of the hydrogen bonding between humectants and H2O improves moisture retention by minimizing water loss due to evaporation.
These ingredients are used in many products, especially those designed for consumers with dry, damaged hair. While they can provide benefit in certain circumstances, it is important to understand how they work and under what circumstances they might provide less-than-optimal results. When considering whether to use humectants, the most important piece of the puzzle is how the weather can impact your hair and the performance of these molecules.