4 Sodium Lauryl Sulfate/Sodium Laureth Sulfate: This is a cheap, very harsh detergent used in many shampoos for its ability to cleanse and foam. Often derived from petroleum, It causes eye irritations, skin rashes, hair loss, scalp scurf similar to dandruff, and allergic reactions. Lookout when you buy products that contain it, sometimes it’s disguised by the definition: “derived from coconut”.