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The CAOA is dedicated to providing up-to-date guidelines for the safe use of essential oils and aromatherapy products.  Please see our Precautions and Contraindications booklet under Resources for Safety Information at the bottom of this page.

Dose is the Key

Safety of essential oils is dose dependent. An analogy that Robert Tisserand uses is “you can probably safely drink 1 – 2 cups a coffee a day without any ill effects, however if you were to drink 100 – 200 cups of coffee in a day you would become very ill.” Because essential oils are measured in drops, there is a greater risk of overuse – intended or otherwise. In most cases, essential oils work better in lower dilutions however some companies promote the use of a much higher dosage.

Chemical Makeup

Safety is dependent upon the chemical makeup of the essential oil. For instance, Cinnamon Bark Essential Oil is high in a constituent called cinnamaldehyde. Cinnamaldehyde can be a dermal irritant or sensitizer (dose dependent). It can also cause toxicity in the kidneys and liver with chronic use. Some citrus essential oils such as bergamot, grapefruit, lemon and lime contain a chemical constituent called a furanocoumarin which can be phototoxic. This means that when these essential oils are applied to the skin which is then exposed to UV Rays, the skin will burn more quickly. Essential oils high in terpenes tend to oxidize more quickly than others which can cause skin irritation.

Mode of Application

Safety is dependent upon the mode of application used. Oral use poses the highest risk and is not recommended except under the care of a qualified health practitioner trained in aromatherapy or a Certified Clinical Aromatherapist who has been trained in the safe use of ingestion. It is important to note that oral application is not approved in North America and most aromatherapy associations have come out strongly against oral dosing. Additionally, oral use is not covered by liability insurance in North America.


Inhalation presents a very low risk to most people. Even in a relatively small closed room, and assuming 100% evaporation, the concentration of any essential oil (or component thereof) is unlikely to reach a dangerous level, either from aromatherapy massage, or from essential oil vapourization. Tisserand and Young (2013) state “the only likely risk would be from prolonged exposure (perhaps 1 hour or more) to relatively high levels of essential oil vapor which could lead to headaches, vertigo, nausea and lethargy”.

Oral Use of Aromatherapy Oils

Essential oils should not be put in drinking water or undiluted in the mouth. This can damage the esophagus and the lining of the stomach. Furthermore, this practice is the least likely to work on a condition, because it is often immediately excreted through feces.

In countries where ingestion of essential oils is permitted, the highly trained aromatherapy practitioners or medical professionals will dilute the essential oil and put it into a slow release gel cap or enteric coated tablet for ingestion. Note: Clinical Aromatherapy Practitioners have medical training over and above an aromatherapy certification course i.e. nurse or physician trained at an appropriate clinical level.

Dermal Application and Safety

Redness or a Rash

If a person experiences redness or a rash after applying an essential oil to their skin, this is NOT the body detoxing. It is a symptom of irritation or sensitization (see below). This most often occurs when an essential oil is applied undiluted to the skin but can also occur if someone has sensitive skin.

Irritation vs Sensitization

There seems to be confusion around these terms. Even seasoned aromatherapists will use the term sensitization to mean irritation. The two reactions are very different, and it is important to note that sensitization is much more serious than irritation.


While some essential oils are classified as potential skin irritants they may not provoke a reaction in everyone. Conversely, a person may have an idiosyncratic reaction to an essential oil that is considered safe for the skin. It is recommended that a person with sensitive skin do a patch test on a small area of skin before using the essential oil(s). This can be done by applying the essential oil(s) at double the concentration they would normally be used to the inside of the forearm (place drops on a bandage and then apply bandage to the skin). Leave for 24 – 48 hours. If there was irritation, it will present as redness, itchiness, swelling or blistering. Essential oils with high proportions of either aldehydes or phenols are often the culprits in provoking irritation.

Moderate Irritants

We recommend using these essential oils in a lower dilution or in cases of sensitive skin, perhaps avoiding them all together.

Damaged or Diseased Skin

Damaged or diseased skin is usually more permeable to essential oils and may be more sensitive to dermal reactions. This can include but is not limited to skin conditions such as eczema and psoriasis and thinning skin due to age or medications. It is always potentially dangerous to apply undiluted essential oils to the skin and in those with damaged or diseased skin, the skin condition can be worsened.


This is a systemic reaction and autoimmune response which usually manifests initially as a rash but can also cause headache, respiratory distress and in extreme cases anaphylactic shock. Once a person has experienced sensitization to a particular essential oil, they will likely always have an adverse reaction to that essential oil.

Recommended Dilution Rates

When an essential oil blend is going to be applied fairly liberally to the body- for example by way of a lotion, carrier oil, gel, hydrosol or water, the following dilution rates are recommended.

Location Dilution
Adult Body 1% – 4%
Adult Face 0.2% – 1.5%
Adult Body & Face During Pregnancy 1%
Also, refer to CI’s during pregnancy and breastfeeding
Nursing 1%
Body Massage 1.5% – 3%
Specific Areas 4% – 10%
Pain/Wounds 5% – 20%
Elderly* 1% – 2%
Children 10+ years 1% – 4%
Children 5 – 10 years 1%- 2%
Children 2 – 5 years 1%
Babies 6 months – 24 months .5%
Infants birth – 6 months (Caution with eo’s used) 0.25%
* Elderly – when determining the dosage for the elderly, whose bodily systems have started to slow down, it is best to use ½ the normal concentration of essential oils normally used for an adult.

Other Dilutions

Application Dilution
Massage oil or lotion Full Body – 3-4 drops into 15ml of lotion or carrier oil – = 1%
Localized application 6 drops in 10ml of lotion or carrier oil = 3%
Compresses 2 – 4 drops of essential oil(s), diluted in a carrier oil, in water
Salves or ointments 3 – 4 drops of essential oil(s) per 5ml of base = 3% – 4%
Facial creams 1 – 2 drops of essential oil in 10ml of cream = .5% – 1%
Inhalations 3 – 5 drops in a diffuser, humidifier or vapourizer (usually in water). In a large room increase to 5 – 8 drops. Inhaler stick – up to 20 drops essential oil(s)
Shampoos, shower gels, bubble baths 12 – 50 drops per base = .25% – 1%
Salts Generally, 10 drops per cup of salts but less if the essential oil is potentially irritating. Remember that essential oils are lipophobic and therefore will not blend well with the salts. You will need to add the essential oil to a carrier oil or an emulsifier prior to blending with the salts.
Sitz Bath Add 5 drops of essential oil(s) to either a carrier oil or salts + a carrier oil and soak in the bath for 5 – 10 minutes.


  • Acute toxicity refers to poisoning by way of ingesting or the absorption of too much essential oil at one time.
  • Chronic toxicity occurs when a small amount of a potentially toxic essential oil is repeatedly applied over a period of time and is thus damaging the body in some way or when any essential oil is used in excess over a period of time. Toxicity can also occur if a person has either liver or kidney impairment or disease.
  • Toxicology also includes the study of hazards related to pregnancy and cancer, skin allergy and/or phototoxicity, liver and kidney dysfunction, effects on the CNS and the endocrine system and damage to the eyes.
  • Although some people may experience idiosyncratic reactions to particular essential oils, in general toxicity is dose dependent. However, there are some instances where even low amounts can produce severe reactions such as allergies and phototoxicity.

Children and Poisoning


Although we do not know the consequences of drinking large amounts of essential oils, there have been documented cases of poisoning with the essential oils of citronella, clove, eucalyptus, pennyroyal, sassafras, wintergreen and wormseed. In most cases, the drops were given accidentally, by mistaking it for another, safer preparation.


Inhalation through the nose of solutions containing either menthol (4 cases) or cineole (9 cases) have been reported to have non-fatal but serious toxicity in children. The ages in these cases ranged from 1 month to 3 years. The effects of poisoning included irritated mucous membranes, tachycardia, dyspnea, nausea, vomiting, vertigo, muscular weakness, drowsiness and coma. The most serious case was that of a child under 2 months of age who had 1ml of a menthol solution introduced into his nose. Essential oils used in humidifiers or diffusers are usually safe for children if one takes into consideration dosage/age amounts and avoids the essential oils listed above.


Avoid the use of the essential oils listed above. Do not use essential oils high in 1,8-cineole on or near the face of children under the age of 5 years (this applies to dermal and inhalation methods) and always follow the recommended dilutions listed above.

General Safety Tips

Essential oils should be labelled clearly to indicate the contents and concentration of the essential oil. Essential oils should be sold in bottles which are fitted with a drop dispenser. And essential oils should always be kept out of reach of children. If a child is suspected of ingesting an essential oil, call your local Poison Control Centre. As well, to dilute the essential oil, any dairy product, ideally one high in fat, can be given to the child (or adult for that matter) immediately after ingestion, however this does not take the place of seeking medical attention.

Therapeutic Grade

About “Therapeutic Grade” Essential Oils: There is no regulatory body in the world that regulates “grades” of essential oils. This is simply a marketing term. One company has even gone so far as to trademark the term “certified therapeutic grade essential oils” – again this is just a marketing term and does not equate to quality.


Adulteration of essential oils is more common than ever before. In the past 10 years, usage of essential oils has multiplied by the thousands. To give an example, a company which launched in 2008 had 3,000,000 independent distributors by the end of 2016. Such massive use of essential oils has placed a strain on essential oil and carrier oil bearing plants as well as causing a sustainability issue. Adulterated essential oils pose a higher risk of adverse reaction.

Essential Oils and Medication

Some essential oils are contraindicated with specific medications. For instance, some essential oils should not be used if a person is on blood thinners. Essential oils high in a chemical constituent called eugenol can be contraindicated when taking Tylenol or Anacin.

Statement on Raindrop Technique (RDT) and Aroma Touch

Raindrop Technique (RDT), Aroma Touch and similar techniques do not meet the criteria for safe practice, as defined by the CAOA Standards of Practice. There have been reported adverse effects regarding RDT, in particular.

Resources for Safety Information

  • CAOA Precautions and Contraindications
  • Essential Oil Safety 2nd Edition – Robert Tisserand and Rodney Young
  • Atlantic Institute Safety Information and Adverse Reaction Reports
Order your printed copy by clicking here.

Facebook Groups about Aromatherapy Safety

Questions You Can Ask

  • Is the person who is recommending an essential oil or blend of essential oils to you a Registered or Professional Aromatherapist and do they carry liability insurance?
  • How long have they been practicing aromatherapy?
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