Hamamelitannin Worst Irritant Oil Control Hamamelitannin at a glance Present in witch hazel A tannin with antioxidant properties Can denature skin Skin-sensitizer with repeated use Hamamelitannin description Hamamelitannin is a tannin that is found in witch hazel (AKA _Hamamelis virginiana_). Tannins are potent antioxidants, however, they also have the ability to denature proteins on skin when used consistently. This can result in skin barrier impairment as well as sensitization. Related ingredients: Witch Hazel Hamamelis Virginiana