Fructooligosaccharides
FOS
No meaningful concern for most people; irritation is possible but rare.
Also written as: FOS · Fructo-oligosaccharides · Oligofructose
What it is
Fructooligosaccharides are short chains of fructose units, usually made from chicory root or sugar beet. They dissolve readily, bind water like other small sugars, and are best known as a prebiotic - a food source that selected friendly bacteria can use. In cosmetics they are added to masks and essences aimed at supporting a balanced skin microbiome.
What it does well
Acts as a prebiotic that may shift the balance of skin microbes
A 2025 review found that prebiotic oligosaccharides including fructooligosaccharides can modulate the skin microbiome when applied topically, but the clinical evidence for visible skin benefits in healthy skin is still preliminary.
Limited evidence
Worth knowing
Microbiome claims run ahead of the evidence
"Prebiotic" on a mask is not the same as a demonstrated improvement in skin condition. The ingredient is harmless and mildly hydrating; the microbiome story is plausible but not yet proven for cosmetic use.
Matters most toAnyone paying a premium for a microbiome-positioned mask.
Where the EU stands
No specific restriction
Not restricted under the EU Cosmetics Regulation; it appears in no annex and has no concentration limit.
Sources (1)
Every link goes to the original: a journal, a PubMed record or an EU document.
- [1]Prebiotic Oligosaccharides in Skin Health: Benefits, Mechanisms, and Cosmetic Applications
Antioxidants (Basel) · 2025 · doi:10.3390/antiox14060754
Review of oral and topical prebiotic oligosaccharides, including fructooligosaccharides, concluding they can modulate the skin microbiome but that cosmetic clinical evidence remains at an early stage.
