Aveda salons in particular use dyes that are plant-derived and use fewer oxidative dyes, which some link to cancer as well. You're usually in good hands at a salon, however - experienced stylists have chemical mixing down to a science and can advise you on your alternatives, if you'd like to use more natural ingredients. How you color your hair may have an impact on your risks for chemical absorption and risks. If you like highlights, then very little dye touches your scalp when using the foil method, minimizing risk. However, if you do a single-process color - one uniform color all over - then the dye has more access to your scalp and can be more readily absorbed. If you color your own hair at home, then choose a brand that's heavy on the plant-based ingredients, like Garnier, which uses grapeseed oil as a conditioner and protectant. You should always consider your allergies and sensitivities before coloring yourself or having a stylist do it.