There are various opinions on how much essential oil to add to a carrier oil. Below are suggestions (from other sites) you might use as a guide to determine the maximum and minimum amounts of essential oils to use with a carrier. Most importantly, unless using an essential oil as spot treatment for a problem area (a drop on the end of a Q-tip), don’t rub or force copious amounts of essential oil directly on the skin. The skin will swell, become red and feel very sore. Then it will likely take a few days, to a week, of vitamin E treatment to heal.