Pharmaceutical grade means the product is over 99% pure, with no fillers, binders or dyes. The Australian government grades Tea Tree oil before it ever leaves the continent on a basis from a pure, medicinal quality pharmaceutical grade, to a harsh, industrial-type cleaning grade. Healing Tree uses only pharmaceutical grade Tea Tree oil, which is over 37% terpinol (an aromatic oil) and less than 4% cineol (an oil found in eucalyptus), making it the safest, most soothing, least irritating Tea Tree oil available.