Dandelion can be a potent allergen, especially if you suffer from hay fever/pollen/ragweed allergies. Dandelion extract is used in skincare and cosmetics for its apparent astringent and soothing properties. It’s used in concentrations of 5-10%. According to one (biased) source, dandelion is a water soluble extract that’s also anti-inflammatory, soothing, anti-irritant. It (may) have a prebiotic and antioxidant effect. However, I am unable to find any scientific studies that prove these effects when applied topically.
Archives of Dermatology, January 1999, pages 67–70