Aluminum Starch Octenylsuccinate

Aluminum Starch Octenylsuccinate is a synthetic powder used as an absorbent, thickener, and anti-caking agent.

As an absorbent, it is great at mattifying skin by soaking up the oil. This is why you'll find it in a range of products from makeup to moisturizers.

This ingredient is considered a modified starch. Starch can also be found naturally in plants.

One study from 1991 found that 5% of this ingredient enhanced titanium dioxide SPF by as much as 40%. The study found 1% titanium dioxide had a 5.6 SPF and adding 5% of aluminum starch octenylsuccinate boosted it to an SPF of 8.1

Although “aluminum” in an ingredient name can raise red flags for some consumers, the form and usage context matter significantly. For typical topical applications, there is no substantial evidence of health risks - such as cancer, neurotoxicity, or systemic “aluminum overload.”