This section is from the book "The Home Hand-Book of Domestic Hygiene and Rational Medicine. Volume 2.", by J. H. Kellogg, M.D.. Also available from Amazon: The Home Hand-Book of Domestic Hygiene and Rational Medicine, Volume 2.
Loss of color of the hair is due to a failure of the papillae to secrete the usual amount of coloring matter. A hair rarely loses its color; hence grayness, or loss of color, begins at the root of the hair.
There is no remedy but dyeing, and that is by no means always safe, since all the popular hair dyes contain lead or some other substance of a poisonous nature. Cases of lead poisoning from the use of hair dyes are by no means uncommon. The following hair dye is recommended by the eminent Professor Hager which may be used with perfect safety: Subnitrate of bismuth, one ounce; glycerine, fifteen ounces. Heat together in a water-bath for an hour. Add carefully a strong solution of caustic potash, while stirring the solution, until it becomes clear. Then add a very strong solution of citric acid until the test paper shows the mixture to be nearly neutral. Add sufficient rose or orange-flower water to make two pints. Color slightly with aniline, as desired.