I'm sure everyone has heard The Legend of The Four Thieves but in case you haven't.
The legend is that during the Bubonic Plague in Europe the homes of stricken or dead people were robbed. It seems that the people who committed the theft didn't get sick. When they(four alchemist)were caught and asked to divulge their secret in exchange for leniency, they said they used a formula consisting of essential oils, herbs and spices.
My recipe consists of the following essential oils: lemon, cinnamon, eucalyptus, clove and rosemary. I also add eucalyptus leaves. Every winter I make soap and room spray using the recipe.