This article was created for the website of the Czech Aromatherapy Expert Society.
Pressed citrus oils, with their burst of refreshing scents and therapeutic properties, invite incorporation not only into aromatherapy blends but also into cosmetics and perfumes. Unfortunately, due to their natural components, furocoumarins (FCs), they can cause irritation when the skin is exposed to sunlight and UV lamps (even up to 18 hours after application!), resulting in a phototoxic reaction. This manifests as phototoxic dermatitis, with symptoms such as pain, redness, blisters, and pigmentation.
Phototoxic reaction and IFRA regulation
How and why does it happen? FC molecules can bind to DNA of skin cells when the skin is exposed to UV radiation. This causes cell death, which results in the unpleasant reaction mentioned. Thanks to the intervention of IFRA (International Fragrance Association), there have been legislative restrictions on the use of citrus oils in cosmetics and perfumes. This was also one of the main reasons why distilled citrus essential oils started to be produced, as they contain little to no FCs, or the amount is negligible.
What are furocoumarins or furanocoumarins (FCs)?
Furocoumarins are natural components of essential oils extracted from the bark of citrus fruits. The most well-known is bergapten in bergamot oil and citropten in lemon, bergamot, and lime oils. However, FCs are also found in other essential oils beyond citrus ones, such as angelicin in angelica, methoxsalen in rue, psoralen in bergamot, pot marigold, angelica oils, and bitter orange oil, as well as marmesin and 8-hydroxybergapten in Visnaga(khella).
Margarita dermatitis and other specificities
A notable aspect are the phototoxic compounds, which are not classified as furocoumarins but are worth mentioning. These include alpha-terthienyl in the marigold oil and dimethyl anthranilate in mandarin leaf oil, as with these essential oils, dermal limits should be observed during skin application. Another interesting component is hypericin, found in the beautiful red macerate from St. John’s Wort flowers, which causes a phototoxic reaction only after internal ingestion; in essential oils, this heavy molecule is not present. R. Tisserand, Essential Oil Safety, 2nd edition, s. 417). I must also mention well-known plants that can cause irritation due to their FC content. Be cautious when handling celery tops, parsley, and wild parsnip. Or the notoriously known “Margarita dermatitis” from the beach, when squeezing limes and lemons releases FCs from the peel into the juice, which then comes into contact with our skin. When sunlight, which is unavoidable during beach stays, is added, a phototoxic reaction occurs. For images of its effects, see the Tisserand Institute website.
Transfer of furocoumarins
Furocoumarins are present in these essential oils in small proportions, approximately between 1-2%, but even 0.1% can be phototoxic. FC molecules are non-volatile, heavy, and therefore larger than most other molecules in essential oil components. R. Tisserand mentions that it is very likely that the heavier FC molecules can also be transferred into CO2 extracts and absolutes. R. Tisserand, Essential Oil Safety, 2nd edition, s. 87). Therefore, it is stated that not only the essential oil from marigold is phototoxic, but also its absolute. Similarly, the absolute from fig leaf is also considered phototoxic.
Distilled citrus oils
Phototoxic reactions to perfumes containing bergamot oil were first recorded in 1916. Over the years, scientists gradually pointed out the connection between FCs and UV radiation. Thanks to IFRA’s efforts and their publication of safety recommendations for citrus oils, this has rarely occurred since the 1970s. All these factors led to the industrial production of distilled citrus oils. They are characterized by a more delicate scent and are completely colorless. Pressed citrus oils, on the other hand, are colored and have a richer aroma, but also contain FCs, which impose dermal limits when applied to the skin. R. Tisserand points out that distilled citrus oils are safe and non-phototoxic. R. Tisserand, Essential Oil Safety, 2nd edition, s. 87Especially because the non-volatile, heavier FC molecules do not pass into the essential oil during the distillation process! Therefore, these essential oils contain virtually no FCs and are not phototoxic. (R. Tisserand: Phototoxicity: essential oils, sun and safety, 20.6.2023)
Safe non-phototoxic citrus fruits according to R. Tisserand:
Distilled essential oils: Bergamot, Grapefruit, Lemon, Lime, Mandarin, Orange
Pressed essential oils: Sweet or blood orange
Other essential oils: Lemon leaf, Neroli, Petitgrain
Likely slightly phototoxic according to R. Tisserand:
Tangerine, Mandarin (fruit), Parsley, Ginger, Yuzu, Patchouli
Distilled versus pressed
Of how and why distilled citrus oils are considered safe, science continues to inform us. For example, an HPLC (High-Performance Liquid Chromatography) analysis of distilled lemon oil shows that it contains 12 times less isopimpinellin, 22 times less bergapten, and 930 times less citropten than pressed lemon oil. This means that distilled lemon oil is not phototoxic, even though it contains some FCs.
Horrific consequences
Conversely, improper use of pressed lime oil as part of a homemade deodorant in coconut oil can lead to adverse reactions, and I recommend checking the Adverse Reaction database at the Tisserand Institute for details. Or, a truly very unfortunate use of undiluted pressed bergamot oil before entering a sauna, followed by a tanning session, can have terrifying consequences. I caution that this is a very unpleasant sight.
Professionalism above all
Finally, it should be noted that the dermal limits according to IFRA 50 and 51 for pressed citrus oils apply only to cosmetics and perfumery. I personally recommend that professionals, including aromatherapists committed to a professional approach to client health, pay attention to their updated versions. Practical tables can also be found in the second edition of Tisserand & Young (2014) – Essential Oil Safety. If you are interested in distilled citrus oils or prefer them in your practice, I recommend the diverse product range of distilled citrus oils from the family company SoZoLe Rose. Here, you will also find pressed citrus oils from smaller Italian growers and distilleries. This gives you the opportunity to easily compare different types and choose exactly according to your needs.
Sources:
Tisserand & Young (2014). Essential Oil Safety 2e. Churchill Livingstone, Edinburgh.
R. Tisserand: Phototoxicity: essential oils, sun and safety (20.6.2023) https://tisserandinstitute.org/phototoxicity-essential-oils-sun-and-safety/
Li, G., Xiang, S., Pan, Y. et al (2021). Effects of cold-pressing and hydrodistillation on the active non-volatile components in lemon essential oil and the effects of the resulting oils on aging-related oxidative stress in mice. Frontiers in Nutrition, 8(June), 1–15 .
https://doi.org/10.3389/fnut.2021.689094
Adverse Reaction Report Details – lime expressed oil https://tisserandinstitute.org/adverse-reaction-database/#home/adverse-reaction-report-detailed-view/5909ab1aac4d112661576d4e/
Adverse Reaction Report Details – bergamot expressed oil https://tisserandinstitute.org/adverse-reaction-database/#home/adverse-reaction-report-detailed-view/5909a23d6000582668659041/
Index of IFRA Standards – 51st Amendment
IFRA Standards
https://ifrafragrance.org/safe-use/standards-documentation
IFRA Complete Standars 50th
