In the U.S. all ingredients must be listed using the INCI (International Nomenclature of Cosmetic Ingredients) name. You are allowed to put the common name/term for that ingredient in parenthesis if necessary, but the FDA requires the INCI names for any and all ingredients. Most cosmetic ingredient suppliers will list the INCI names on product pages for your convenience.
Ingredients are also required to be listed in descending order from most to least used. Fragrance & colorants don't count and can be placed at the very end of the ingredient list in any order.
Example: If I use 3oz Olive oil, 1oz apricot kernel oil, .50oz babassu oil, 3.5oz water, .25oz cedarwood essential oil, 2oz gold mica (contains titanium dioxide and iron oxide)... the label would read:
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Water (Aqua), Olea Europaea (Olive) Fruit Oil, Prunus Armeniaca (Apricot) Kernel Oil, Orbignya Oleifera (Babassu) Seed Oil, Cedrus Atlantica (Cedarwood) Bark Oil, Mica, titanium dioxide, iron oxide
I believe you can describe them as pure essential oils in your item listings as long as your oil didn't come pre-mixed with any sort of carrier oil or extra ingredients. Just be sure not to make any sort of drug or treatment claims.
Resources:
http://www.fda.gov/cosmetics/resourcesforyou/industry/ucm388736.htm
http://www.fda.gov/cosmetics/productsingredients/products/ucm127054.htm
http://www.soapqueen.com/bath-and-body-tutorials/lip-products/labeling-your-products-lip-balm/