As pure as possible means that WECOLOUR hair dye does not contain ammonia and PPD. In stead of PPD we use TDS (Toluene-2.5 Diamine sulfate). TDS is less agressive and about 30% of people who are allergic to PPD tolerate TDS. But WECOLOUR hair dye is still a chemical product. We recommend you to always carry out an allergy test.