The Patch Test
You should never use essential oils directly on your skin, they should be diluted first. One way to test your blend on yourself, or the person who you are making a blend for, is called a Patch Test.
To perform the Patch Test, you will apply a drop of the oil (or blend that you created) on the inside of the forearm.
Cover the drop with a simple bandage and wait 24 hours. After the 24 hour waiting period, remove the bandage and see if there was any reaction on the skin.
If there was no reaction, this means that you (or your client) is most likely not sensitive to the oil, or blend that you have created.