A Natural Molecule
Mannitol is a natural molecule (type of sugar alcohol), which can be found in marine algae, in vegetables such as pumpkins, celery and strawberries, and in the exudate of shrubs and trees, such as the manna ash and olive tree.
Mannitol is known to act as humectant and moisturizer. Therefore it increases the moisture content of the skin and keeps it soft and smooth.
Additionally, humectants increase the active ingredients' ability to penetrate skin.
Additional important but unknown properties of Mannitol are the antioxidative properties and with this the protection from environmental stresses such as blue light or UV radiation. 1
Due to its antioxidative potential, the addition of Mannitol has a protective effect on structural components in the skin and delays the degradation caused by radicals.2
1 Botta et al., Genotoxicity of visible light (400–800 nm) and photoprotection assessment of ectoin, L-ergothioneine and mannitol and four sunscreens, J PhotochemPhotobiol B. 2008 Apr 25;91(1):24-34
2 André and Villain. Free Radical Scavenging Properties of Mannitol and Its Role as a Constituent of Hyaluronic Acid Fillers: A Literature Review Int J Cosmet Sci . 2017 Aug;39(4):355-360.