Extract derived from the plant Betula alba (aka white birch). It can have potent antioxidant properties, but can also have astringent properties, which makes it a potential irritant for skin if it is one of the main ingredients in a product. It’s also used as a fragrance ingredient.
Likely a similar ingredient to Betula Platyphylla Japonica, which is used in Asian skincare and also commonly referred to as white birch.
Journal of Agricultural Food Chemistry, October 1999, pages 3954–3962