With summer just around the corner and warmer, sunnier days hopefully ahead of us, I thought it would be helpful to explore phototoxicity and look at the common aromatherapy oils that are known to be phototoxic. 

Phototoxicity, also known as photo-irritation, is skin irritation caused by phototoxic chemical substances following exposure to light. When phototoxic substances such as coumarins or furanocoumarins are applied to the skin they can cause an excessive response to sunlight or UV rays, resulting in redness that looks like an exaggerated type of sunburn. Blistering may also occur in severe cases. 

While these chemicals can be found in suntan preparations and a range of toiletries, they are also found in some aromatherapy products. For instance, although aromatherapy is generally considered a safe complementary health therapy treatment, there are some essential oils (and other herbal oils) that contain furanocoumarins, albeit in small amounts. Nonetheless, when applied topically, these chemical substances are absorbed into the skin, where their molecular structure allows them to absorb and store UV light, before releasing it in a burst on to the skin which causes irritation. Even if essential oils are well diluted, a person can still experience phototoxicity if their skin is exposed to sunlight, and more so if they expose their skin to sunbeds or very strong sunlight. 

This article aims to provide information on some of the oils that can be used safely, and which ones really ought to be avoided if you’re planning to go out in direct sunlight or use sunbeds.

The most common phototoxic aromatherapy oils

Most of the known phototoxic oils come from the Rutaceae and Apiaceae families.

Belonging to the Rutaceae family, citrus oils, such as Lemon, Lime, Grapefruit, Mandarin, Orange, and Bergamot are considered stimulating, energising and uplifting and are an excellent choice for promoting wellbeing. Indeed, as I’ve said in previous blogs, Bergamot is often described as ‘Happiness in a bottle’, helping to reduce stress and improve the mood. It is important to note however that Bergamot, as well as some of these other citrus oils are regarded as phototoxic. 

Phototoxicity is largely dependent on whether the essential oil has been extracted from the plant material (fruit peel) using expression (cold-pressed) or steam distilled. 

For example, citrus oils which have been steam distilled are not thought to be phototoxic and include: Lemon (Citrus limonum) and Lime (Citrus aurantifolia). While Bergamot, (Citrus bergamia), Lime (Citrus aurantifolia), Orange Bitter (Citrus aurantium), Lemon (Citrus limonum), and Grapefruit (Citrus paradisi) which are expressed from plant material are considered phototoxic. Conversely, other essential oils which are expressed but are not phototoxic include: Mandarin, (Citrus reticulata), Orange Sweet (Citrus sinensis) and Tangerine (Citrus reticulata). 

Other phototoxic essential oils include Angelica Root (Angelica archangelica) and Cumin (Cuminum cyminum) from the Apiaceae family, and Tagetes (Tagetes patula, T. minuta, T.erecta) from the Asteraceae family.

It is also important to remember that other aromatherapy products can be phototoxic too. For example, Hypericum oil (Hypericum perforatum) also known as St John’s Wort, is reputed to be soothing, anti-inflammatory, antiseptic and analgesic, useful for mild burns, bruising and minor wounds. Nonetheless, it may also cause photosensitivity when used on fair-skinned and/or sensitive skin. As a cautionary measure, I would, therefore, recommend covering the skin prior to exposure to sunlight when using this particular herbal oil.

Risk of photoxicity

The risk of phototoxicity is reliant not just on the chemical substances present in an oil but also the amounts. For example, Tagetes essential oil (Tagetes patula, T. minuta, T.erecta) is considered 100 times more phototoxic than expressed Grapefruit (Citrus paradisi).

Mixing several phototoxic essential oils will, of course, increase the risk of phototoxicity, so this should be considered when blending. Please also remember that citrus oils usually have terpenes in significant amounts. However, this chemical component is sometimes removed from the oil. When this happens, it means that there is a higher concentration of the remaining chemical components, such as furanocoumarins, which will affect the maximum use levels for managing phototoxicity risk. I would, therefore, recommend purchasing citrus essential oils that are not deterpenated.

According to Tisserand & Balacs (1995), there is no risk of phototoxicity if aromatherapy products that contain phototoxic essential oils are used in soaps, body washes and shower gels that are washed off the skin before exposure to sunlight or UV rays. Please note, however, this only applies to wash-off products as opposed to those that may come into contact with the skin in a sauna or steam-room. 

Some experts also suggest that there is no risk if you apply phototoxic essential oils to the skin and then cover those areas up before going outside. It is important to note however that summer clothes tend to be lightweight and light in colour, meaning that UV rays can penetrate them, unlike more heavyweight, dark winter clothing. Applying sunscreen may, of course, also help reduce the risk of phototoxicity. 

Time can obviously affect phototoxicity too. For example, the intensity of the skin reaction will increase during the first hour after application, remain at a peak for the next 60 minutes and then gradually reduce over a period of eight hours. Tisserand & Balacs (1995) suggest that this is due to the length of time it takes for the phototoxic chemical substances to penetrate through the top layers of the skin into the lower levels. To be safe, experts generally recommend not exposing the skin to the sun or UV lights for at least 12 hours after applying aromatherapy products containing phototoxic chemical components.

As noted above, coumarins and furanocoumarins are the most common chemicals to cause phototoxicity. Arguably, the best-known chemical constituent is bergapten, a derivative of psoralen, the parent compound of the family known as linear furanocoumarins. Bergapten, as the name suggests, is found in Bergamot essential oil. While phototoxic chemicals are comparatively non-volatile, which means that they do not easily vaporise, they can be greatly reduced in, for example, Bergamot oil. It is possible to buy Bergamot which has had the furanocoumarins removed, which greatly reduces the risk of phototoxicity. Look out for oil that is labelled Bergamot FCF which means it is furanocoumarin-free.

Just as an aside, some aromatherapists believe that the fragrance of Bergamot FCF essential oil is of a lesser standard to that in which the furanocoumarins have not been reduced. You may, therefore, wish to use the ‘whole’ oil in a diffuser or a burner instead so that you can still enjoy the original aroma. Indeed, inhaling essential oils is often regarded as the most effective way to benefit from them therapeutically and this is supported by scientific research. For example, studies show that inhaling essential oils has an influence on the limbic part of our brain that deals with emotions. For instance, female patients undergoing dental work reported less anxiety when inhaling Sweet Orange during treatment, whilst another study found that patients suffering from depression required less antidepressant medications after citrus fragrance treatment.

Recommended maximum use levels

IFRA guidelines indicate the percentage dilution at which phototoxic essential oils are considered safe to use on the skin (see table 1 below), with a higher percentage dilution believed to carry a risk of phototoxicity (Tisserand & Balacs,1995). 

When calculating essential oil concentrations, I find it helpful to remember that generally speaking 20 drops of essential oil equates to 1ml. Therefore, as an example, 0.7% of Lime (Citrus aurantifolia) will be achieved by blending 7 drops of the essential oil in 50ml of carrier oil. This can be calculated as follows: 50ml x 20 drops = 1000 x 0.7% = 7.

Table 1: Maximum % dilution levels

* Please note that in general 2.5% strength is recommended for an aromatherapy blend and comprises of a ratio of 1:2, meaning 1 drop of essential oil to every 2 ml of carrier oil.

I hope that you’ve found this blog useful and that it will help you stay safe in the sun this summer.

Christine Fisk                                  
Consultant Aromatherapist           

Disclaimer & Safety Advice

Read other articles by Christine Fisk

References

Tisserand, R., & Balacs, T. (1995). Essential Oil Safety A Guide for Health Care Professionals. Churchill Livingstone.