By default, citrus essential oils are photosensitizing. That is, if you apply them to your skin, they greatly enhance the effect of the sun on your skin, meaning you are very likely to get a burn.
A story I like to tell to illustrate this is from my earlier days of DIYing. I know about the photosensitizing effects of citrus essential oils, but figured it couldn’t be too bad. I made a batch of lotion (~125mL/half a cup) and added four drops of tangerine essential oil. I put some on my arms and went for a 20 minute bike ride at about 8am on a cloudy day in Calgary, Canada. I got a burn. Granted, I am pretty pale, but I would not normally get a burn under such conditions.
Some citrus essential oils have been treated to remove their photosensitizing compounds. Bergapatene-free bergamot essential oil is one example. Some suppliers also say their 5-fold citrus essential oils are no longer photo toxic due to extended processing, but I recommend checking with your supplier there. Otherwise, it is best to assume that any citrus essential oil should not be used (and left) on the skin.
Litsea cubeba, lemon myrtle, and lemongrass essential oils are great alternatives—they smell citrussy, but are not sensitizing.
Posted in: Ingredients