Carrier oils, also called base oils, or fixed oils - are one way essential oils can be blended to achieve a lower concentration for topical use on the skin. Their role is to help “carry” the essential oil onto the skin, at a more tolerable and safer concentration for use on the skin.
Carrier oils are usually derived from fruits and nuts, butters, or vegetable sources. They differ from EO’s in that they contain fatty solids, emollients, antioxidants and other nutritive properties. It is the carrier oil that delivers the "oily" feel, not the essential oils.
Quality carrier oils for the skin will be manufactured by cold pressed processes; vs. heat extracted, cold pressed oils often contain Vitamin E, and natural antioxidants helping to prevent spoilage of the carrier. Cold pressed oils can be stored in the refrigerator to help extend their shelf life, and will soften or become liquid again at room temperature – do not microwave, this can destroy active ingredients!
Avoid using any synthetic, chemical or petroleum based carriers with essential oils.