We present a novel skin reflectance model for faces and its application to face appearance editing. We decompose the high-dimensional bidirectional scattering surface reflectance distribution function (BSSRDF) of skin into components that can be estimated from measured data. Our model is intuitive, amenable to interactive rendering, and easy to edit. High-quality renderings come close to reproducing real photographs. We have measured 3D face geometry, skin reflectance, and subsurface scattering for a large group of people using custom-built devices and fit the data to our model. The analysis of the reflectance data reveals variations according to subject age, race, gender and external factors (heat, cold, makeup, etc.) We derive a low-dimensional model using non-negative matrix factorization (NMF) that spans the space of skin reflectance in our database. A user can define meaningful parameters in this space- such as race, gender, and age- and change the overall appearance of a person (e.g., making a Caucasian face look more Asian) or change local features (e.g., adding moles, freckles or hair follicles).