Solanum Tuberosum Starch

Solanum Tuberosum Starch is potato starch, the same fine white powder used in cooking, refined and milled for cosmetic use. Solanum tuberosum is simply the botanical name for the potato, and the INCI name is a good example of a very ordinary ingredient looking unfamiliar on a label.

It belongs to a family of plant-derived starches used in cosmetics alongside rice, corn and tapioca starch, all of which do broadly similar jobs. They are used as absorbents, as bulking agents and as texture modifiers, and they exist mainly to change how a product feels rather than to do anything to the skin itself.

On an ingredients list it appears as Solanum Tuberosum (Potato) Starch or as a modified version such as Aluminum Starch Octenylsuccinate, which is treated to make it more water-resistant and free-flowing. You will find it in loose and pressed powders, dry shampoos, mattifying primers, deodorants, masks and mineral makeup.

It is very well tolerated. Starches are chemically simple, non-irritating and fragrance-free, which is why they turn up so often in products aimed at sensitive skin. The one caveat worth knowing is that starches are a food source for microorganisms, so they need a competent preservative system in any product containing water, and they are best kept dry.

Potato starch works physically rather than chemically. The granules are absorbent, taking up oil and moisture from the surface of the skin, which is why a starch-containing powder reduces shine and helps makeup stay put. It is a straightforward soaking-up effect, not a change in how much oil the skin produces.

Its second role is textural. Starch granules are small and roughly spherical, so they roll against one another and give products a soft, silky, slightly powdery feel. Formulators use this to take the greasiness out of a rich cream, to give a primer its blurring finish, or to make a pressed powder apply smoothly. In mineral makeup it also helps disperse pigments evenly.

Because it sits on the surface and does nothing biologically, it neither treats nor irritates. That inertness is precisely why it is used: it is a way of adjusting how a product behaves without introducing anything active into the formula.

Potato starch is a formulation ingredient rather than a step in a routine, so there is little to do beyond knowing what it signals.

• Seeing it on a label tells you the product is likely to have a soft, dry or mattifying finish.
• Useful for oily or combination skin in the form of primers, powders and mattifying products through the day.
• It absorbs oil, it does not reduce it. If shine returns quickly, that is normal and not a failure of the product.
• Keep powders dry. Damp fingers or brushes introduce water into a product that is not designed for it.
• Very well tolerated, including by sensitive skin, and free of fragrance or common irritants.
• Not a substitute for skincare. A mattifying powder manages the appearance of oil; it does not address why skin is producing it.