How Essential Oils And Fragrances Cause Sensitization And Fragrance Intolerance

Essential Oils And Fragrance Sensitization


It is paramount to know how to use essential oils correctly.

Improper usage can cause lasting (possibly permanent) side effects and immune sensitization.

In this post, we will discuss how to use essential oils properly and potential sources of hidden essential oils.


  1. Basics Of Essential Oils And Fragrance Intolerance
  2. My Experience With Sensitization
  3. Types Of Sensitization And Symptoms
  4. Potential Sources Of Hidden Essential Oils And Fragrances
  5. Problematic Essential Oils
  6. Noteworthy Problematic Fragrances
  7. Most Potent Human Skin Sensitization Fragrances
  8. More Problematic Fragrances
  9. Risk Factors Of EO-Induced Immune Sensitization
  10. Mechanism Of Action

Basics Of Essential Oils And Fragrance Intolerance

Essential oils have strong bioactive properties and although they are considered as safe and nontoxic when used at low concentrations, essential oils and their compounds may possess a strong allergy potential. R

Sensitization can happen when an essential oil is not diluted well enough and enters the body (methods of absorption listed in below section).

This sensitization may cause permanent immune priming to terpenes, terpenoids, and fragrances (fragrance intolerance). R R

My Experience With Sensitization

A while back, I had a problematic experience with thieves oil (ingredients): 

  • Cinnamomum verum (Cinnamon) bark oil
  • Citrus limon (Lemon) peel oil
  • Eucalyptus radiata (Eucalyptus) leaf oil
  • Rosmarinus officinalis (Rosemary) leaf oil
  • Syzygium aromaticum (Clove) bud oil

Foolishly, while using it to clean mold, I did not dilute it well enough and inhaled the terpenes and got a lot on my skin.

This gave sensitization (neurological symptoms) to the above products and now I have to be careful being exposed to any of the ingredients found in thieves oil.

I have heard very similar stories with multiple clients that have fragrance intolerance and chemical sensitivities. 

Types Of Sensitization And Symptoms

EO-induced sensitivities can cause:

  • Allergy Contact Dermatitis - hypersensitivity (CD4+ T-lymphocytes react) after 48 to 72 h after exposure to the allergen R
  • Ataxia R
  • CNS Depression - within hours after exposure and lasting up to 3 days R
  • Eczema R
  • Paresis R
  • Phototoxicity - increased hypersensitivity to UV radiation/sunlight R
  • Neuropathy R
  • Tremors R

Potential Sources Of Hidden Essential Oils And Fragrances


Potential Sources

Here is a list of potential sources of essential oils:

  • Chewing Gums and Mints R
  • Cigarettes with flavoring agents R
  • Cleaning Products and Soaps R
  • Cosmetics - If such a product is not explicitly labelled as “fragrance-free”, “contains no perfume” or “scented-free” it can be assumed that it contains fragrance chemicals R
  • Creams - certain creams that have EO's in them may be worse than others depending on if it has free oil or oil loaded lipid nanoparticles R
  • Essential oils - includes absolutes, aromatic waters and concentrates, concretes, steam distillation, cold pressing, resinoids, supercritical fluid extracts, or pomades R
  • Food Products - such as candies, jam, ice cream, pudding, baked goods, and yoghurt R R
    • They can be used to induce the flavor of pineapple, raspberry, peach, grapefruit, plum, red apple, lime, watermelon, orange and lemon R
  • Insecticides R
  • Mouthwash-Products R
  • Perfumes R
  • Pharmaceuticals R
  • Products with Fragrance - such as scented trash bags R
    • May be labeled a variety of names, such as "aroma" or "flavour" R R
  • Shampoos R
  • Toothpastes R R

Absorption Into The Body

They can be absorbed into the body a few ways:

  • Body Contact - epidermis, hair system, nails, lips and external genital organs R
  • Inhalation - fat soluble chemicals may reach the blood faster through skin contact vs inhalation. R
  • Orally - through teeth or mucous membranes of the oral cavity R

Product Quality

It is important to note the some essential oil (cheaper brands) may be incorrectly produced and have low quality ingredients: R

  • Adding of single raw materials
  • Adding cheaper essential oils of the same plant but from another country—adjuncts
  • Adding of cheap synthetic compounds (identical to natural) isolated from other oils
  • Adding of individual synthetic substances to oils and aromatic raw ingredients
  • Labelling one essential oil as another
  • Blending with less expensive essential oils of the same plant taken from a different part of the plant

Problematic Essential Oils

Noteworthy essential oils to consider:

  • German Chamomile - derived from Matricaria chamomilla
    • Barely any reports of contact allergy or allergic contact dermatitis have been described in the scientific literature R
  • Immortelle - derived from Helichrysum italicum
    • Has very little literature on inducing contact dermatitis. R
  • Lavender - derived from Lavandula angustifolia (lavender) or Lavandula latifolia (Spike lavender)
    • Once oxidized has higher chance of inducing allergy R
  • Neroli - derived from Citrus aurantium (bitter orange)
    • Has shown in case studies to induce phototoxicity R
  • Peppermint - derived from Mentha piperita (peppermint),  Mentha aquatic (watermint) and Mentha spicata (spearmint)
    • Has shown to induce allergies in a few case studies R R
  • Rose - derived from Rosa damascene, R. canina, R. centifolia, R. galica, R. moschata and R. rugosa
    • Four cases of allergic contact dermatitis to rose essential oils occurred in three aromatherapists and in one chemist with a particular interest in aromatherapy R
  • Rosemary - derived from Rosmarinus officinalis
    • An aromatherapist, a physiotherapist and a masseur were diagnosed with occupational contact dermatitis due to exposure to rosemary oil R
  • Tea Tree - derived from Melaleuca alternifolia (Maiden et Betche), Cheel (narrow-leaf tea tree), M. linariifolia Smith (flax-leaf tea tree) or M. dissitiflora F. Muell (creek tea tree)
    • Multiple case studies showing contact allergy R
    • When oxidized, can become a potent skin allergen R
    • In animal review,more than 400 dogs and cats developed tremors and other problems of the nervous system after administration of 0.1–85 mL of tea tree oil orally or onto the skin R

Noteworthy Problematic Fragrances

These are the some noteworthy fragrances:

  • Anethole - found in anise, anise myrtile and fennel oil
    • 3 case studies with cheilitis - caused pain, persistent itch, blistering lips, intra-oral burning sensation, dry mouth and loss of taste (from toothpaste and ) R R R
  • Bisabolol/levomenol - found in German chamomile
    • Case reports describe multiple patients with a history of intolerance to moisturizers and balms with bisabolol R R
  • Carvone - found in various oils but mostly commonly caraway, spearmint and dill
    • Taken topically, it has shown to cause skin hypersensitivity R R
    • Taken orally, it may cause oral lichen lesions R R
  • Citral - found in lemongrass, verbena, citronella, orange and lemon oil
    • 9 massage therapists that were directly exposed to the citral oil while massaging their clients suffered from hand dermatitis R
  • Eugenol - found in clove, allspice, Ceylon cinnamon, nutmeg, basil and pepper
    • Is hepatotoxic (in high  concentrations) R
    • Case study of a 34-year-old woman using eugenol in a cleaning product developed asthma, maculopapular erythema, cough and dyspnoea, which needed to be treated with antihistamines R
  • Farnesol - found in citronella, neroli, cyclamen, and tuberose oil
    • High prevalence to cause dermatitis R
  • Geraniol - found in rose, citronella, palmarosa, lemon, geranium, bergamot and lavender oil
    • Oxidized geraniol may cause an allergic reaction R
  • Limonene - found in oranges
    • Oxidation can cause dermal sensitization R R
  • Linalool/coriandrol/licareol - found in spearmint, rose, cypress, lemon and cinnamon
    • When oxidized, can cause dermal sensitization and eczema R R
  • Menthol/levomenthol - found in peppermint or mint oils
    • In case studies has shown to induce allergic contact cheilitis R

Most Potent Human Skin Sensitization Fragrances


More Problematic Fragrances

Even though all essential oil in high enough exposure length and dosage can cause sensitivity, these fragrances (listed below) have a higher chance of inducing sensitivity: R

  • Amylcinnamal
  • Amylcinnamyl alcohol
  • Anisyl alcohol
  • Benzyl alcohol
  • Benzyl benzoate
  • Benzyl cinnamate
  • Benzyl salicylate
  • Cinnamyl alcohol
  • Cinnamal
  • Citral
  • Citronellol
  • Coumarin
  • Eugenol
  • Farnesol
  • Geraniol
  • Hexyl cinnamicaldehyde
  • Hydroxy-citronellal
  • Hydroxy-methylpentylcyclohexenecarboxaldehyde
  • Isoeugenol
  • d-Limonene
  • Linalool
  • Methyl heptin carbonate
  • 3-Methyl-4-(2,6,6-tri-methyl-2-cyclohexen-1-yl)-3-buten-2-one
  • Oak moss and treemoss extract
  • Treemoss extract
  • 2-(4-tert-Butylbenzyl) propionaldehyde

Risk Factors Of EO-Induced Immune Sensitization

Having a lower body weight may predispose to greater risk of developing major illness from essential oils (animal study). R

Mechanism Of Action

Fragrance substances can act as haptens (prehaptens or prohaptens) that form allergens that are more potent than the parent substance by activation outside or in the skin via abiotic (chemical and physical factors) and/or biotic activation, thus, increasing the risk of sensitization. R

This problem is worse with oxidation of the products as well. R