One of my favorite ways to use an essential oils is what is called Jump Starting.
Place a drop of the oil on your index finger and rub it into the buccal lining of the cheek. That means the inside of your cheek behind your teeth. You can also put it under the tongue but it has a higher chance of hitting one of the taste buds of the tongue and may not taste too good!
Put a drop inside the cheek every minute for 10 minutes,, then every 10 minutes for one hour, then every hour your are awake for the rest of the day. If still needed the next day then take a drop by mouth every few hours until the problem is finished.
I would like to say that I would only drop pure therapeutic grade essential oils into my mouth. I would not drop brands that you are not sure on the distillation process of that oil. Do not use oils that have been distilled any other way than steam distillation. Young Living Oils uses steam distillation for their oils. I only use this brand of oils for all my oil needs!
Also their is a list of GRAS ratings for the oils. Some oils are too hot to drop in the mouth undiluted and can burn the mouth. Some of these oils are oregano and lemongrass. Generally, Young Living Oils sends the GRAS ratings out with their shipments. If you don't know the GRAS ratings then ask the company to send you a pamphlet about it. The ratings are also in the Essential Oil Desk Reference published by Essential Science Publishing.