If the recipe is for application somewhere very sensitive, like the eyelids, I would not add an essential oil at all.
Otherwise, generally speaking you want to stick to 1% or less for the face and 2–3% or less for the body. Make sure the recipe has an oil phase so the essential oils will be properly dispersed. If the formula you’d like to add essential oils is entirely water-based you will need to include a solubilizer as well to ensure the essential oils are safely diluted in the end product.
You’ll also need to make “room” for the essential oils by reducing another ingredient in the recipe by however much you’re adding. So, if you are adding 1% essential oils to the recipe, you would want to use 1% less of something else—typically something liquid, like a liquid oil or water. In an emulsion I remove the essential oil amount from the water; in an anhydrous product, I remove it from the predominant carrier oil.
Also: find out the maximum usage rates for the individual essential oils and make sure you stay within those maximum levels. It very well may not be a full 2% or however much you wish to include. Your suppliers are typically not a good place to determine maximum usage levels for essential oils. The IFRA has a database that contains a lot of information, but isn’t massively user friendly as it mostly focusses on the individual fragrant compounds rather than whole essential oils. If you are interested in working with essential oils I highly recommend investing in a copy of Essential Oil Safety: A Guide for Health Care Professionals by Robert Tisserand & Rodney Young. I’ve also found this page listing 400 essential oils and their maximum usage levels and the rest of the associated website to be quite useful. The levels listed there don’t always jive with EU regulations, but if you aren’t selling in the EU it is a good place to start your research.
Posted in: Troubleshooting & Adjusting