Yes, it is possible to be allergic to even very pure and high quality essential oils!

Anyone who tells you that you cannot be allergic to essential oils or that when skin irritation arises in response to the use of essential oils (for example hives, rashes, itching, etc.) it means that your body is “detoxing” and that you need to continue to use oils is misinformed (please see postscript below about the emotional origin of allergies).

Top quality essential oils do not contain synthetic ingredients or other contaminants. This reduces the chances of adverse reactions. But all essential oils are extremely concentrated and are undoubtedly capable of inducing immediate or delayed hypersensitivity reactions in certain people and under certain conditions. In these instances, the offending substance should be withdrawn immediately.

Essential oils are safe when used according to common sense cautions. They are, however, not a modality where “more is better”. It should be our goal to avoid inducing a hypersensitivity reaction in the first place because in some cases, once stimulated, hypersensitivity can persist for life, thus depriving the affected person of the benefits of that essential oil. For this reason (among others) diluting essential oils may be the most effective and safe option. Although this article will emphasize cautions and points of concern, it is important to remember that essential oils are inherently benign and can be used safely by the vast majority of people, from children to elderly, as long as they are used in reasonable quantities and according to common sense guidelines.

Definitions

According to Mosby’s Medical Dictionary, an allergic reaction is “an unfavorable physiological response to a substance (called an allergen) to which a person has previously been exposed and to which the person has developed antibodies.” According to the same dictionary, an allergen is “a substance, which may not be intrinsically harmful, that can produce a hypersensitivity reaction in the body.”

The nature of allergens

Almost all allergens (whether pollen, dust, dander, or other substances) are proteins or polypeptides. Both proteins and polypeptides are large molecules made up of strings of amino acids. Some polypeptides contain just a few amino acids, while some proteins contain dozens, hundreds, or even thousands of amino acids. But the bottom line is that polypeptides and proteins are large molecules. Essential oils are manufactured by a process of distillation and distillation only allows for extremely small molecules in the finished product. Most proteins and polypeptides are from 100-1000 times larger than the largest compounds found in essential oils.

The absence of polypeptides and proteins in essential oils is the reason that many people are able to use essential oils produced by plants to which they are allergic without any problem. For example, my husband is very allergic to black pepper. If he consumes even the smallest amount of black pepper, his tongue will itch, his throat will swell, and he will sneeze for hours. He can, however, use Black Pepper essential oil without any reaction at all. Mountain cedar is a common allergen to many residents of Central Texas. The cedarwood essential oil we use is distilled from the same plant, but it does not trigger an allergic reaction in many who are allergic to mountain cedar pollen, whether it is applied topically or used aromatically.

It is the absence of polypeptides and proteins in essential oils that causes some people to claim that it is impossible to be allergic to an essential oil. Unfortunately, however, the truth is more complicated than that.

Circumstances  under which essential oils can act as allergens

Phenols

While the vast majority of allergens are protein or polypeptide in nature, phenols are one type of compound found in essential oils which can, in some cases, elicit a true allergic response. Potentially allergenic phenol compounds found in essential oils include phenolic ethers, phenolic sesquiterpenes, and phenolic diterpenes. Examples of essential oils that contain these substances include:

  • Clove
  • Fennel
  • Basil
  • Cypress
  • Clary Sage

Haptens

Some essential oils contain compounds that can act as haptens. A hapten is a small, reactive molecule that, when combined with a skin protein, can cause the formation of antibodies and lead to an allergic reaction. This means that certain essential oils are capable of eliciting a true allergic response, even though they do not contain polypeptides and/or proteins themselves.

It is difficult to predict which essential oils will act as haptens, but it does seem clear that oxidized essential oils are much more prone to induce allergic contact dermatitis, perhaps by acting as haptens. Essential oils become oxidized when they are exposed to air and this process is sped up by exposure to heat and/or UV light. For this reason, essential oils should be stored in amber or other colored glass bottles and should be kept in a temperature-controlled and ideally dark environment. For maximum shelf life, consider storing your essential oils in the refrigerator. Do not leave essential oils in your car or other circumstances where they will be exposed to high heat and keep essential oils in the smallest possible container (to minimize contact with air).

Essential oils that are more likely to cause sensitization if oxidized include:

  • Black pepper
  • Citrus oils (lemon, lime, grapefruit, bergamot, and wild orange)
  • Cypress
  • Fennel
  • Frankincense
  • Jasmine absolute
  • Juniper berry
  • Melaleuca
  • Rose
  • Spruce (found in Balance blend)

Keep in mind that, even when kept under ideal conditions, essential oils do not last forever. According to Robert Tisserand, consider discarding opened bottles of essential oils after:

  • Citrus, Lemongrass, Frankincense, Melaleuca, and Spruce oils – 1-2 years
  • Virtually every other essential oil – 2-3 years
  • Sandalwood, Vetiver, Patchouli – 4-8 years

How do you know when an oil is oxidized? Often citrus oils will become cloudy or develop sediment at the bottom of the bottle. Oils that were originally blue will turn greenish. The oil will not smell as fresh as it once did (although, because oxidation takes place gradually, it can be hard to perceive the change in odor without comparing the essential oil to a freshly opened bottle).

Possible skin reactions

Essential oils can induce three types of skin reactions:

  • Irritation
  • Sensitivity, aka contact dermatitis
  • Photosensitivity

Irritation

An irritation reaction occurs very rapidly, within seconds to minutes of exposure. When irritation occurs following exposure to essential oils, typically the reaction is non-allergic in origin. This type of reaction typically causes a red wheal or burn and the sensation associated with this type of reaction is heat or burning. The most common cause of this type of reaction is an essential oils that is high in phenols (for example oregano, clove, or thyme) or aromatic aldehydes (for example cinnamon).

To manage this type of reaction, immediately dilute the offending oil by applying a carrier oil and follow up by washing with warm water and plain soap. Do not wash first with water, as this will push the oil deeper into the skin. Generally this type of reaction can be avoided by diluting “hot” oils to no more than 2-5% strength.

Sensitization, aka allergic contact dermatitis (ACD)

This type of reaction develops over time — multiple exposures to the offending oil are required. At the first exposure, no reaction is evident. But then with subsequent exposure(s) (sometimes even after days, months, or even years of use), a rash or hives develop. In severe reactions, other signs such as sneezing and shortness of breath may be evident as well.

Patient characteristics that increase the risk for the development of ACD:
  • Use of multiple medications.
  • Compromised antioxidant status (due to inadequate diet or chronic illness).
  • The presence of other allergic conditions, such as asthma, eczema, and/or hay fever.
  • Application of essential oils to damaged, inflamed, or irritated skin.
  • Psychological stress.
  • Advanced age (peak incidence around age 60).
  • Female gender.
  • Personal or family history of dermatitis
Variables of application that increase the risk for the development of ACD:
  • Highly concentrated or neat application of essential oil(s). The key factor here is “dermal loading” or the dose per unit area of skin exposed. This means that one drop of essential oil applied to one square inch of skin is much more likely to cause ACD than one drop of essential oil applied to one square foot of skin.
  • Frequent application of essential oil(s). Repeated exposure to the same essential oil over time increases the risk of developing ACD.
  • Use of certain essential oil(s) that are more likely to trigger ACD. Certain essential oils are more likely to trigger ACD than others.
  • The presence of contaminants or adulterants in the essential oil(s).
  • The use of oxidized or denatured essential oil(s). See the list above of essential oils that are more likely to trigger sensitization when they are oxidized.
  • The use of isolated chemical constituents from essential oil(s), as opposed to intact essential oil(s) with the full complement of naturally-occurring components present.
  • The use of essential oils in combination with synthetic chemicals that act as irritants. Examples of such chemicals include surfactants in soaps and synthetic preservatives.
  • Application conditions that result in enhanced absorption of essential oil(s). These conditions include things like covering the site of application with an occlusive dressing, applying heat on top of the application site, and using sensitizing essential oils in conjunction with “driver” oils such as peppermint or blends containing peppermint.

Photosensitivity

Photosensitivity is an interaction between a component in the essential oil, the skin, and UV photons. Photosensitivity reactions can range in severity from slight darkening of the skin at the site of application to the development of a blistering burn. The development of a photosensitive reaction is delayed, with a peak at 36-72 hours after UV exposure. Post-inflammatory skin-darkening may persist for weeks or months after the acute inflammatory phase.

The most common chemical component in essential oil that causes photosensitivity is furanocoumarins. These substances are found mainly in cold-pressed citrus oils, including:

  • Bergamot (the most likely to cause photosensitive reactions)
  • Lemon
  • Lime
  • Grapefruit
  • Wild Orange

Note that when citrus oils are prepared using steam distillation, the photosensitizing chemical constituents are excluded and therefore the resulting essential oil will not trigger a photosensitive reaction.

Exposure to UV light should be avoided for 12-18 hours following the application of most citrus oils and for up to 72 hours following Bergamot oil. The safest practice is to avoid applying photosensitizing oils to skin that is exposed to light and to avoid applying Bergamot oil to the skin altogether (it can be used safely via diffusion).

Common sense cautions for avoiding skin irritation with essential oils

  • When possible, dilute essential oils, especially in patients at risk for developing ACD.
  • Always dilute “hot” oils such as oregano, thyme, clove, cassia, and cinnamon before applying them to the skin.
  • If a rash, irritation, or itching develops following essential oil exposure, stop using essential oils until the problem clears up.
  • Use the lowest effective concentration, particularly when you are using essential oils on an ongoing basis.
  • Use special caution if you fall into a category that places you at higher risk for developing ACD (above).
  • Protect essential oils from oxidation by replacing caps immediately after use, keeping them in amber glass containers and preferably in a dark location, protecting them from heat, keeping them in the smallest possible container to minimize exposure to oxygen, storing them in the refrigerator, and discarding them according to the time frames above (or sooner if you see or smell evidence of oxidation).
  • Do not apply photosensitizing oils to skin that is exposed to UV light. Do not apply Bergamot essential oil to the skin at all.
  • Eat a healthy diet and take supplements in order to maintain good antioxidant status.
  • Consider using essential oils internally rather than topically (if appropriate), as sensitization is less likely to occur with the internal use of oils.
  • Avoid using essential oils along with other cosmetics or chemicals, as these other products may potentiate sensitization.
  • If you are a person who is prone to the development of ACD (above), avoid conditions that enhance the absorption of essential oils, such as covering the site of application with occlusive dressings, applying heat over the site of application, or using “driver” oils such as peppermint along with other oils.

Postscript

Regarding the emotional origin of allergies — I absolutely believe that emotions can play a role in the development of allergies. In fact I think of allergies as a phobia of the immune system, which gives me important insight about how to handle them.

Imagine a person who has a phobia of snakes. No sane or compassionate individual would attempt to fix this problem by placing the phobic individual in a dark closet with a pile of writhing of snakes (like a bad reality TV show). To do so would induce out and out panic and would virtually guarantee that a minor phobia would become lifelong and severe.

In the same way, a person who has developed a sensitivity to an essential oil should NOT continue to be exposed to that oil in a misguided attempt to “detox”. Instead we should wait until the reaction has completely settled down and the body and the immune system is generally in a calm state. Then the oil can be reintroduced in a VERY gradual and cautious way (in small quantities, not on consecutive days, etc), always watching for evidence of a reaction.

Please refer to this excellent article from the Tisserand Institute for more information on this important topic.

References:

Essential Oil Safety, 2nd edition by Robert Tisserand and Rodney Young. Churchill Livingstone, 2014.

Clinical Aromatherapy: Essential Oils in Practice, 2nd edition by Jane Buckle. Churchill Livingstone, 2003.

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