Young living makes 98% of the 2% of essential oils that are suitable for medicinal purposes in North America.
The key to producing therapeutic-grade essential oils is to preserve as many of the delicate compounds within the EO as possible. Constituents can be affected by the plant which the oil was produced, soil conditions, fertilizer, geographic region, climate, altitude, harvesting methods, and distillation processes.
Young Living uses only plant material free of herbicides and agrichemicals. These chemicals can react with the EO during distillation to produce toxic compounds. Many pesticides are oil-soluble so they can mix into the EO. YL tests EVERY BATCH OF OIL yet only 28% of all oils are accepted and bottled!
Some scary news: the FDA only requires that 5% of the named essential oil to be in the bottle in order for it to be labeled "pure", so it's important to know the source of your oils!!
Young living allows and encourages everyone to visit their farms and take part in their harvests. I LOVE THAT!