As you may have read here, high quality essential oils are highly concentrated. For example, it takes the rind from two lemons to make just one drop of lemon essential oil. Typically your body doesn’t need that much essential oil to get the therapeutic benefits and diluting the essential oil with a carrier oil is a safe and effective option (and it saves a bit of money too).
The first reason to dilute essential oils is that your body often does not need a whole drop (or more) of essential oils applied topically in order to benefit. When you consider that one drop of lemon essential oil is equal to 2 lemons and that one drop of rose essential oil can be equal to the petals of as many as 60 roses, it becomes apparent that one drop of high quality essential oil can go along way. Essential oils can be diluted with any fatty oil or natural lotion product and the same benefits will be experiences. In fact, in some cases, especially sleep, too much essential oil can actually produce the opposite effect.
Another reason to dilute essential oils is safety. Some essential oils are very gentle, but there are some that aren’t and pose specific risk. For example, these essential oil singles (and any blend containing them) are phototoxic if not diluted at very high levels: angelica, bergamot, cassia, ginger, lemon, lime (cold-pressed lime), and orange. This means that if applied to skin undiluted or not diluted enough, these essential oils will interact with sunlight on exposed skin and cause illness or injury (burn). Additionally, some oils are “hot” oils, which means that they feel hot to the skin when applied (or have a heating and cooling sensation. “Hot” oils include: oregano, cinnamon, clove, thyme, cassia, and peppermint. These and other essential oils may cause skin irritation if applied without a carrier oil. The safe way to apply essential oils for daily us is to always use a carrier oil, even with gentle oils. This practice will save you money and potential risk.
The last reason to dilute is cost savings. Essential oils will last longer when diluted. While a drop of lemon essential oil can be pretty cheap (about 4 cents), the cost of one drop of rose essential oil is considerably more (about $2.25). Making each drop last longer can produce small and large cost savings in addition to being safe and effective.
Each carrier oil also has properties (similar to essential oils, but not as impactful). Read more about carrier oils and their properties here.