Few essential oils are used neat, but are mixed into a fixed plant oil base like Almond, Grapeseed or Coconut.
(Fixed oils do not evaporate quickly on exposure to the air like essential or volatile ones.)
These base or carrier oils contain certain benefits themselves, not least their contents of iodine and vitamin E. They also act as a balancing and stabilizing agent. A carrier or base oil should be pure, and preferably cold pressed when it retains its essential vitamin content better. It should have little or no smell of its own, and it should be penetrative. The quantities of essential oil to base oil will vary a little from oil to oil, but unless otherwise stated you should use 2-3 drops essential oil to 5 ml (1 tsp) base oil for use on the body, and 1 drop essential oil to 5ml (1 tsp) base oil for the face