Hydrating Shampoos

Haidressing shampooing a client's hair
Photo: Dean Bertoncelj/Shutterstock
Q: How do hydrating shampoos work?
A: To answer this properly, we have to explain a little bit of the chemistry behind how shampoos in general work.
Most shampoos (in their simplest forms) contain surfactants. The term "surfactant" stands for "Surface Acting Agent". These surfactants are compounds that include molecules with "lipophilic" (oil-attracted) ends and "hydrophilic" (water-attracted) heads.
These compounds are spread along the surface of the hair in the shampooing process and the lipophilic ends attach themselves to the oils on the hair and when the rinse step occurs, the hydrophilic heads are pulled along with the water and drag the oils away with the compound.
Now, shampoos will also contain substances to smooth the cuticle and held the condition of the hair. These can be silicones which smooth the cuticle, or moisturizers that simply add moisture to the hair itself. These moisturizers work well, but the moisture is easily dispersed from the hair once again through normal stresses.
But some better shampoos and conditioners contain humectants, which are compounds that contain several hydrophilic groups. These humectants are hygroscopic substances and absorb water from their environment. So, the shampoos containing these humectants deposit the humectants into the hair, and the humectants then help the hair absorb and retain moisture from the water in the shampooing process and the other moisturizing ingredients.
Some common humectant compounds include: glycerine, propylene glycol, and glyceryl triacetate.
See also:
How shampoo works
Can hair have too much moisture?
The need for hydrating shampoo in winter
Hair care