Pullulan

How it works

Pullulan is a polysaccharide produced by fermentation with the fungus Aureobasidium pullulans. Its chain has an unusual regularity that lets it dry into a clear, continuous film with very low oxygen permeability, which is why the same material shows up as the edible film in breath strips and as a coating in food and pharmacy.

Two jobs follow from that. In the bottle it thickens water-based formulas and helps keep suspended material in place. On skin it dries into a thin film, and as the water leaves, the film contracts slightly and pulls on the surface. That pull is the instant tightening a certain kind of mask or serum is selling. It is a real physical sensation and it belongs to the film rather than to the skin: rinse the film away and it goes with it. Because pullulan is water-soluble, plain water is enough to do that — unlike the silicone and acrylate films used where durability is the whole objective.

The evidence

As a film-former and thickener it does exactly what it says, and there is nothing controversial about it. It is a long-established food-grade material with a good tolerance record on skin.

Claims that reach beyond film-forming deserve more care. The immediate smoothing and tightening are measurable in the sense that anyone can feel them, and they are also entirely temporary. Where a product offers that sensation as evidence of firming, a feeling is being asked to stand in for an effect it does not have. Pullulan sits on the surface, has no route into the dermis, and makes no lasting change to what is under it.

Suitability

• Broadly well tolerated, since it rests on the surface rather than penetrating
• Films can feel tight on already-dry skin, which is a comfort question rather than a safety one
• Common in wash-off masks, sheet-mask essences and anything promising an immediate visible result
• Not an active: it changes how a product behaves, not how skin behaves

Concentration

No figure is given, and a figure would not tell you much. Film-formers are used at whatever level produces the film the formulator wants, which depends on the rest of the water phase. A higher level means a stronger film and a tighter feel, not a better product.

Conflicts & combinations

Nothing conflicts with it chemically. The practical caution is layering: films are the layers most likely to roll and pill when something is rubbed over them before they have set, so a pullulan-containing layer wants a moment to itself before the next one goes on.