Phototoxic essential oils – list and characteristics

What is phototoxicity of essential oils?

Phototoxicity ( increased sensitivity to sunlight ) is a skin reaction that occurs after the application of certain chemicals and subsequent exposure of the skin to UV radiation (e.g. sunlight).

In the case of essential oils, phototoxicity is most often caused by compounds from the furanocoumarins group – photosensitizing molecules present mainly in cold-pressed citrus oils. Highly phototoxic furanocoumarins include psoralen , its derivatives such as 5-methoxypsoralen (bergapten) and 8-methoxypsoralen (xanthotoxin, also known as methoxsalen) , as well as related coumarins such as oxypseudoin and limetin (citropten) . Some oils also contain other phototoxic compounds outside the furanocoumarins group – for example, marigold oil (Tagetes) contains alpha-terthienyl (a thiopene compound), and petitgrain oil from mandarin leaves (Citrus reticulata) contains dimethylanthranilate (anthranilic acid methyl ester).

Phototoxicity mechanism: Furanocoumarins and related phototoxic ingredients absorb the energy of UVA rays in the skin, which activates them to their triplet state and allows them to form bonds with the DNA of skin cells This leads to cell damage and death, and an acute inflammatory reaction – photodermatosis . This manifests itself as skin redness (erythema) resembling a severe sunburn , and in more severe cases, blisters . These changes typically develop within 1–2 days of sun exposure and may peak after 36–72 hours. This can result in hyperpigmentation (skin discoloration) in the affected areas, lasting for up to several months. Unlike a photoallergic reaction, phototoxicity is a predictable and dose-dependent phenomenon—it will occur in everyone with sufficiently high exposure to a given compound and UV.

Extraction and the Risk of Phototoxicity: The method of extracting the oil is a significant factor. Cold-pressed citrus oils (from the peel) retain the furanocoumarins present in the raw material, which is why many of them are phototoxic. Oils obtained by steam distillation, on the other hand, contain negligible amounts of these compounds – the heavy furanocoumarins molecules do not significantly transfer to the volatile fraction during distillation. As a result , distilled citrus oils (and special FCF versions – furocoumarin-free ) are not phototoxic. For example, bergamot oil free of bergaptene (so-called Bergamot FCF) retains its fragrance but no longer causes a phototoxic reaction. Similarly, distilled lemon and lime oil do not contain photosensitizing doses of furanocoumarins. .

It should be emphasized that not all citrus oils are phototoxic - for example, sweet orange, mandarin or tangerine (even pressed) have negligible levels of furanocoumarins and do not usually cause photodermatoses In addition to citrus fruits, several oils from other plant families, especially Rutaceae and Apiaceae , exhibit phototoxic properties .

"Not every citrus oil is phototoxic – the method of extraction and the presence of specific compounds, such as furanocoumarins (e.g., bergapten, psoralen, methoxsalen, oxypeucedanine), are crucial. Citrus oils pressed from the peel of the fruit may contain these substances and exhibit phototoxicity, while distilled oils – e.g., from leaves or flowers – are naturally free of them.
Limonene, although it dominates the composition of most citrus oils (up to 94%), does not pose a risk of phototoxicity. This is why, for example, sweet orange and tangerine, despite their high limonene content, are not phototoxic – they contain negligible amounts of furanocoumarins. Neroli oil (from the flowers of the bitter orange tree, Citrus aurantium ) is obtained by steam distillation and does not exhibit phototoxicity .
Petitgrain oil (Bigarade) (from the leaves and young twigs of the same plant) is also distilled and free of furanocoumarins, making it completely safe for skin applications – even in daytime products .
Mandarin (Citrus reticulata) and tangerine (its cultivar) are other examples of oils pressed from the peel that are nevertheless not phototoxic , as they contain only trace amounts of furanocoumarins (or none at all). In contrast, pressed bergamot, pressed lime, pressed grapefruit, cumin, and angelica root contain significant amounts of phototoxic compounds and should be used with extreme caution or avoided before sun exposure . Distilled versions (e.g., FCF bergamot , distilled lime , distilled lemon ) do not contain furanocoumarins and are safe for daily use. Conclusion? The decisive factor is not the type of fruit, but the method of extracting the oil and the specific chemical compounds present in a given extract. Phototoxicity is not a characteristic of "citrus oils" per se—it is a characteristic of selected components present in specific oils pressed from the peel. – Based on the Tisserand Institute.

The following is a list of essential oils considered phototoxic based on the scientific literature and data from Essential Oil Safety (R. Tisserand & R. Young) . For each, the Polish and Latin names, the main phototoxic chemical constituents, typical skin effects, recommended safe concentration limits for topical preparations, and whether the distilled version of the oil is phototoxic are listed.

List of phototoxic essential oils