Pullulan is a polysaccharide produced by Aureobasidium pullulans, a fungus, through fermentation of starch. It is unusual among cosmetic polysaccharides for the quality of film it forms.
The film
Most polysaccharides used in skincare hold water. Pullulan does that too, but its distinguishing property is the film it leaves as it dries: unusually strong, flexible, transparent and impermeable to oxygen.
The same properties make it useful well outside cosmetics. Pullulan films are used for edible packaging, for dissolvable breath strips, and for capsule shells.
The tightening effect
This is what most people notice. As pullulan dries it contracts slightly, producing an immediate sensation of tightness and a visible smoothing of fine lines.
The effect is entirely temporary and entirely physical. Nothing is happening to the skin's structure; a film is contracting on top of it. It lasts until you wash, and it is why pullulan appears in products marketed on instant results.
Worth understanding as separate from anything the rest of a formula might do over weeks.
The hydration side
Pullulan also holds water at the surface and its oxygen-barrier property means the film reduces water loss more effectively than most polysaccharide films.
It contributes a smooth, silky slip to texture, which is part of why it appears in products designed to sit under makeup.
Antioxidant claims
Some research reports free radical scavenging activity for pullulan. The evidence is modest, and its role in a formula is realistically the film rather than the antioxidant contribution.
In formulation
Water-soluble, stable across a wide pH range, and used at low concentrations. Frequently combined with other polysaccharides, as it is here, because their film properties differ and complement one another.
Reading a label
Pullulan high in an ingredient list suggests a product designed around immediate visible effect. Lower down, it is more likely contributing to texture and hydration.
