Essential oils are easily absorbed by the skin. The best places to apply essential oils are on the bottoms of feet, spine, forehead and temples and the back of the neck. If there is a particular issue you are dealing with, you can target the oils directly there. So for a headache apply on the temples, for a stomach ache apply around the belly button. To avoid any kind of sensitivity you can dilute essential oils in a carrier oil such as fractionated coconut oil, grape seed oil and almond oil.
SAFETY NOTE
Some areas of the body should be avoided such as the skin around the eyes, eyes and inner ears and broken, damaged or otherwise injured skin.