While not everyone has ready access to scientific analysis of essential oils, these questions can help you determine if a product is therapeutic grade:
Do the fragrances vary from batch to batch as an indication that they are pure and painstakingly distilled in small batches rather than industrially processed and mixed on a large scale?
Does your supplier grow and distill its own organically grown herbs?
Are the distillation facilities part of the farm where the herbs are grown so they are freshly distilled - or do the herbs lose their potency as they wait for weeks to be transported and processed?
Does your supplier use low pressure and low temperature to distill essential oils and preserve all of their fragile chemical constituents?
Are the distillation cookers vertical rather than horizontal?
Are they fabricated from costly stainless steel alloys to reduce the likelihood of the oils chemically reacting with metal?
Does your supplier have representatives traveling worldwide to personally inspect the fields and distilleries where the herbs are grown and distilled?
Does your supplier buy directly from the grower?
Does your supplier scrutinize the facilities to ensure that no synthetic chemicals are used?