D-Beta Fructan is a fructooligosaccharide that is said to boost skin immunity and help to build moisture. It’s a plant sugar that’s also supposed to help the skin take in vitamins and minerals (Return to Beautiful Skin). Fructans in general have been studied for their immune-helping and anti-inflammatory effects, though there aren’t studies on D-Beta Fructaion in particular (Paul Vos).
Generally speaking, researchers are investigating the effects of eating fructans more than putting them on skin and even that research is limited. In terms of consumptions, studies have looked at fructans as a prebiotic — or something that the body doesn’t digest that can be fermented by the flora in the gut (Functional Ingredients).
Overall, it’s not known to be harmful or negative in any way.