George William Askinson, Perfumes and Their Preparation
“ HAIR DYES AND DEPILATORIES.The custom of dyeing the hair is universal in the Orient; in the Occident, however, hair dyes are also frequently used, namely, to hide the grayness of the hair, sometimes to give the hair a preferred color. Hair dyes, which are very numerous, may be divided into groups—those containing the dye-stuff ready formed, and those in which it is produced in the hair by some chemical process. Some hair dyes contain substances which in their nature are decidedly injurious to the hair ”
