Herbert M. Shelton said this quote

“ The skin is an integral part of the body and depends upon the general system for its supply of food and to carry away its waste. Skin health depends primarily upon the general health of the body. All attempts to deal with the skin as an independent entity, without due regard to its reliance upon the general system, must of necessity result in failure. The skin is nourished by the blood and there is no other source from which it can draw sustenance. Skin foods are all frauds. These are composed chiefly of grease. No fat can be assimilated by the skin or other tissues of the body until it has first been broken down into its constituent fatty acids in the process of digestion. Even were this not true, the skin contains very little fat and these skin foods would still not constitute proper nourishment for it. Blood is the only skin food. ”