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A few weeks ago, I began my series on the phototoxic potential of certain essential oils. This is due to a repeat of the unfortunate events stemming from my lax attitude around this topic.

Phototoxic reactions are inflammatory skin responses resulting from application of certain sun-sensitizing essential oils that are “activated” by exposure to UV rays.

The good news is you can take precautions to avoid these unwanted consequences. The most important one is to know which oils can cause this response (see below). Other tips can be found in the previous blog.

However, there’s something that wasn’t discussed. Many of you asked, “What about ingesting these same essential oils?”

Here’s my response after digging a little deeper. *

*(Note: this is my conclusion after exploring the sources listed, consulting with mentors, and from my 17-years of using essential oils in my clinic.)


What Dr. Sarah Found Out Regarding Ingesting Sun-Sensitizing Essential Oils

As a naturopathic and functional medicine doctor, I feel it’s my duty to know about this subject on a deeper level.

For 17 years, I, along with my clients and family, have been ingesting citrus oils in our water. There have been no incidents of skin discoloration from this. The few cases I’ve had with sun reactions have been due to direct application of the commonly known photosensitizing essential oils:

  • Angelica Root Essential Oil
  • Bergamot (Cold Pressed)
  • Bitter Orange (Cold Pressed)
  • Cumin
  • Fig Leaf Absolute
  • Grapefruit (Cold Pressed)
  • Lemon (Cold Pressed)
  • Lime (Cold Pressed)
  • Mandarin Leaf
  • Opopanax
  • Rue
  • Tagetes

(Source: Aromaweb)


Considering Phototoxicity verses Sensitization

In order to help me better understand the concept of phototoxicity from ingestion, I dug back into the topic that comprises of skin reactions to essential oils, sensitization. This is because the question of phototoxicity from ingestion of an essential oil is not what most aromatherapists typically come across. It is more often related to a “skin response” from topical application.

Sensitization was covered previously when I reviewed the subject of allergies to essential oils. There is a heated debate among oilers, as many believe these responses can be avoided by using a carrier oil. Others feel they aren’t related to the use of oils neat (without a carrier oil), but rather linked to several other connecting factors. These include:

  • the quality of the essential oil used
  • predispositions in “sensitive types” (those who have allergies, autoimmunity, and/or have current skin conditions)
  • an interaction with other skin-care products
  • oxidation from poorly manufactured or stored essential oils

The details can be found here, but the fact is some do experience skin responses to essential oils. Although experts may “poo poo” that this could be a “detox response,” I feel that this is an aspect to consider as well. This is because I understand that essential oils are metabolized by liver enzymes and they do have evidence that they can influence “detox” pathways and/or act as antioxidants to protect cellular health. (source, source, source, source, source-under pharmacology)

The bottom line is that essential oils aren’t “allergens,” per se, because they do not contain proteins or amino acids. This means they can’t be the sole cause of a negative skin reaction, something else has to be present. However, they can act as haptens, attaching to proteins or allergic molecules which can contribute to a negative response, usually over time.


Phototoxicity Reactions- The Guilty Furanocoumarins (FCs) Exposed

Due to the fact that no one can argue about unwanted skin discoloration from the sun with certain essential oils, especially yours truly, safety precautions have been delineated. The International Fragrance Association and the Research Institute of Fragrance Materials have come up with standards that state the maximum amount allowed of these various phototoxic constituents in fragrance products, FCs. These can be found here (click on the “+” to read details).  (source, source)

These guidelines provide dilution suggestions for essential oils containing these compounds and is based on skin contact with human volunteers. The oils have been tested by applying a certain amount of them to the skin of subjects followed by exposure to UVA light.

There are variations in the methods to determine when a skin response would occur with various essential oils. For example, the study with orange peel extract was comprised of eight subjects. The researchers examined reactions after 24-48 hours. Next, they tested what concentration would have No Observable Effect Level (NOEL) on miniature swine and rodents and it was found to be at a dilution of 6.25%. After taking both into account and very complicated math, orange peel extract was suggested to be safe to use for humans at a 1.25% dilution level in the sun. (Note: a 1 % dilution would be 6 drops of EO per oz. of carrier oil per Dr. Z’s dilution chart.)

This article provides a wonderful summary of the findings along with dilutions for using sun-sensitizing essential oils outdoors. However, I think it’s just simpler to avoid applying these oils to the skin 12-14 hours prior to sun exposure and taking the necessary precautions already suggested.

Regarding dosage, essential oils contain a very low percentage of these compounds, so one would need to have to use a concentrated amount, or be extremely sensitive, to cause a reaction. For example, bergamot contains about 5% of these non-volatile compounds. This was discussed in this post on potential medication interactions with essential oils. Therefore, we are back on the dosage issue regarding ingestion.


Ingesting Sun-Sensitizing Essential Oils

Dr. Sarah still sips on some lemon water in the sun, but I don’t do more than several drops during a long day at the beach. Here’s why.

Most regulations and understanding of this reaction of furanocoumarins are based on topical application. However, phototoxic reactions have been reported by systemic agents (table 3, source). If one ingests large amounts, or is extremely sensitive, perhaps enough of these substances would be in the blood stream to cause activation. However, the half life is quite short in comparison to most prescription medications.

In conclusion, I agree with Lindsey.

No surprise there.

Bottom line: Phototoxicity due to ingestion of these sun-sensitizing essential oils is possible, but the probability of it happening with with just one or two drops is a very low mathematical gamble.


More Resources:

Get an essential oils consult from me. I apply the philosophy and principles of the naturopathic and functional medicine to guide you with which essential oils and supplements will work best for you!

* Please note that the studies from PubMed aren’t specific for any specific essential oils company.

This material is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness. You should check with your doctor regarding implementing any new strategies into your wellness regime. These statements have not been evaluated by the FDA. (Affiliation link.)

Disclaimer: This information is applicable ONLY for therapeutic quality essential oils. This information DOES NOT apply to essential oils that have not been tested for purity and standardized constituents. There is no quality control in the United States, and oils labeled as “100% pure” need only to contain 5% of the actual oil. The rest of the bottle can be filled with fillers and sometimes toxic ingredients that can irritate the skin. The studies are not based solely on a specific brand of an essential oil, unless stated. Please read the full study for more information.

Thanks Pixabay for the images!