Although my expertise does not lie in hair coloring, I am frequently approached about the subject as some people believe that this topic falls into the category of color cosmetics. So I will comment on what I know about this area and from what I have read. Hair coloring products generally fall into three main categories: temporary, semipermanent, and permanent. All these hair color products, except for temporary color, require a patch test before application to determine if the client is allergic to the product. "Hair lightening" also referred to as "bleaching" or "decolorizing" is a chemical process involving the diffusion of the natural color pigment or artificial color from the hair. All permanent hair color products and lighteners contain both a developer, or oxidizing agent, and an alkalizing ingredient as part of their ammonia or ammonia substitute. The purpose of this is to raise the cuticle of the hair fiber so the tint can penetrate the keratin, facilitate the formation of tints within the hair fiber, and bring about the lightening action of hydrogen peroxide.