The short version
Some citrus essential oils contain natural compounds that can make skin react more strongly to ultraviolet light. When a product containing them stays on the skin and the skin is then exposed to sun or tanning lamps, the result can be unusual redness, a burn-like reaction, or lasting discoloration. These are often called photosensitizing oils, and the reaction is called phototoxicity.
This does not mean citrus oils are unusable. It means they deserve a little understanding, especially in leave-on products.
What causes the reaction
Many citrus oils are pressed from the peel. Peel oils can contain a group of compounds known as furocoumarins (sometimes called furanocoumarins). When these sit on the skin and ultraviolet light reaches them, they can trigger a reaction that looks like a sunburn but may be stronger than the sun exposure alone would suggest. The effect is a direct chemical reaction with light, not an allergy, so it can happen to people with no history of sensitivity.
Which oils are involved varies. Cold-pressed (expressed) oils from the peel of bergamot, bitter orange and lime are among those most often named as a concern, and several other citrus peel oils are treated with caution by various safety references. Sweet orange and some mandarin or tangerine oils are generally described as lower in risk, but references do not always agree, and the products you buy differ from batch to batch. If you are unsure, treat a citrus peel oil as potentially photosensitizing unless a trustworthy supplier or reference says otherwise.
Pressed versus distilled
How an oil is made matters. Cold-pressed citrus oils retain the heavier compounds from the peel. Steam-distilled citrus oils generally leave most of these behind, so they are commonly described as much less likely to cause this particular reaction. There are also products labeled as processed to remove the problematic compounds. Labels differ, so check what the supplier states about processing, and be skeptical of vague claims. Lower risk is not the same as no risk, and a distilled oil can still irritate or trigger an allergy.
Where this matters in homemade products
The concern is greatest with products that stay on the skin and are applied to areas that will be exposed to daylight:
- leave-on lotions, face serum blends and body oils
- balms and lip products
- sprays and mists applied to exposed skin
It is much lower with products that wash off quickly, such as soap, where contact time is short and the product is rinsed away. Even then, caution is reasonable, and the article on scenting soap covers more about how fragrance behaves in a bar. Bathing with citrus-scented products and then going straight out into strong sun is a less common but possible scenario, and the same applies to scrubs and bath salts.
Practical precautions
General steps that many references suggest:
- Check the oil. Find out whether it is expressed or distilled before choosing it for a leave-on product.
- Keep amounts low. Follow a trusted safety reference for maximum concentrations, since limits differ between oils. This site does not give formulas, and the article on essential oil dilution explains why general guidance is better taken from a reliable, current source.
- Avoid sun on treated skin. Leave the product off areas that will be exposed to sun or tanning beds, or choose something else for daytime. A common suggestion is to allow several hours between application and sun exposure, though advice varies by oil and amount.
- Cover up. Clothing over treated skin is more dependable than hoping a low amount is fine. Sun protection is a separate topic, and covering the skin is not a substitute for caution with the ingredients.
- Choose another scent. If the sun is a regular part of the day, consider a non-photosensitizing alternative for leave-on use.
Recognizing a reaction
A phototoxic reaction often appears as redness in the shape of where the product was applied, sometimes with blistering, and it may leave a darker mark that lingers. It tends to show up within hours to a day or two of the exposure. If you suspect this, stay out of the sun, rinse the area gently, avoid applying more of the product, and ask a doctor or pharmacist if the reaction is severe, blistered or slow to settle. Any reaction near the eyes needs prompt professional advice.
A patch test will not reliably reveal this issue, because the skin must also meet ultraviolet light for the reaction to show. That is one reason why the guide to patch testing treats citrus oils as a special case.
Other points about citrus oils
Citrus oils are also known for oxidizing relatively quickly, and an old bottle can become more irritating. Store them tightly closed, away from heat and light, and replace them if they smell off. Like other essential oils, they should never be used undiluted on skin, are not for swallowing, and need extra care around pets, young children and during pregnancy.
The balanced view
Citrus scents are cheerful and popular, so it is natural to want them in homemade products. The way to enjoy them is to know the type of oil, keep amounts modest, use them mostly in rinse-off products, and avoid sun on skin carrying a leave-on blend. When a reference disagrees with another, choose the more cautious position. Outcomes vary between people, and this article is general information rather than medical advice.