Galactoarabinan, abbreviated to GA by botanist types, is a polysaccharide extracted from larch trees. One of its properties is that it reduces particle size, which helps ingredients disperse and, in doing so, can improve the SPF properties of a product with sunscreen. However, it turns out to be much more interesting than this.
GA boosts the immune system and is recognized by the FDA as a source of dietary fiber. Studies have shown it can minimize fine lines, perhaps because it acts as a gentle exfoliant and inhibits moisture loss.
There has been at least one study on inhibiting moisture loss: a 2% concentration of GA on a sample of 21 people. A separate test on 31 people demonstrated that it can exfoliate without irritation: a 5% concentration of GA performed better than 8% lactic acid. This multi-tasker also did well in tests to see if it will irritate human skin.