Hydrating agents increase the water content of the skin and help to maintain its soft and smooth appearance.
Several categories of ingredients make it possible to maintain hydration:
•
Humectant
agents
which retain water thanks to their hygroscopic capability (having strong affinity for water). Among
humectants
:
Urea
, Amino-Acids,
Sodium Lactate
, Glycerol or
Glycerin
, Propylene Glycol,
PEG
(Polyethyleneglycol), and
Sorbitol
.
•
Film-forming
agents
, substances which together with water form semi-permeable hydrogels, less effective in time than occlusive agents, but more acceptable agents because they allow the skin to 'breathe'. Among the film forming agents: Collagen, Elastin, DNA,
Pectin
, Gelatine, Chitosan, the Glycosaminoglycans (like
Hyaluronic Acid
).
•
Occlusive agents
which form an impermeable film on the surface of the skin. Among the occlusive agents: Petroleum Jelly,
Paraffin
, Vaseline Oil, Sweet Almond Oil (
Prunus Amygdalus Dulcis Oil
), Wheat germ Oil, Shea Butter (
Butyrospermum Parkii Butter
), Beeswax (
Cera Alba
).
•
Lyotropic agents
which can retain water thanks to their amphiphilic character: these molecules have at the same time an absorbent part (which has affinity for water) and a hydrophobic part (which does not have affinity for water). Among the lyotropic agents: Lanolin and its derivatives, Ceramides, AGE (essential fatty-acids).