Phototoxicity, sometimes referred to as photo sensitivity, refers to constituents in the essential oil that absorb sunlight intensely...in effect, increasing or focusing the effect of the sun on your skin. It’s a constituent of the essential oil called a furanocoumarin that causes this. (Note: It’s also furanocoumarins that make drinking grapefruit juice problematic with some medicines.)
If these phototoxic essential oils, and/or products containing them, are left on the skin and then exposed to sunlight, they can cause the sun’s effect to be greatly magnified.
This mostly applies to products that are going to stay on the skin - “leave-on” products like lotions, lip balms, perfumes etc. In soaps, in which the product is rinsed off, so little of the essential oil remains behind on the skin that I’ve never heard of it being a problem.
Bergamot is perhaps the most well known phototoxic essential oil. It contains a furocoumarin called bergatptene. Lucky for us, there are bergatptene-free oils that can be used in “leave-on” products. Other cold pressed (not steam distilled) citrus essential oils (like lemon or lime) can be phototoxic as well. But folded oils, like 5-fold orange have had much of the terpenes removed, so they are much less phototoxic.
Here’s a list of the most common phototoxic essential oils. Unless you’re using one of them in your lotion, you should be just fine. But always always always check with your supplier or vendor to make sure you know exactly what the qualities of your particular ingredient is.
I applaud you for always knowing about your ingredients. Many of us got our starts making soap and bath & body products because we wanted to know exactly what we were putting on our skin. If we make products for other people, it’s just as important to know and communicate that to them.
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