Toxic Effects of Essential Oils

Sometimes, essential oils maybe recommended for certain medical conditions like otitis media, severe respiratory or gastro-intestinal infections. Make sure that you get a prescription from a registered MD for such medication for otherwise they could be contaminated with adulterants, pesticides, heavy metals etc. These could cause essential oils toxicity that can prove fatal sometimes. One such oil that Western aromatherapists are warned against is wormseed oil that is acutely toxic and also has skin sensitizing effects. Other nations however do not practice such caution and wormseed is widely used as ethnic or veterinary medicine.

What is Toxicity in Aromatherapy

Toxicity in general refers to the degree to which any substance can damage a non-living or living organism. Toxicity can refer to chemical, biological or physical toxicants. With reference to aromatherapy, essential oils toxicity refers to the misuse of these oils. Toxicity is one of the chief hazards associated with essential oils. The toxic reactions are based on three factors:

  • The amount of the oils being used
  • The method of administration
  • Physiological condition of the person undergoing treatment

Types of toxicity which can occur because of essential oils include:

Acute toxicity

This can occur after a single strong fatal dose has been administered. Acute toxicity is usually oral or dermal. Oral toxicity occurs when essential oils are taken internally and there is an adverse effect. This could lead to poisoning and death. It is this oral intake of essential oils that has resulted in serious cases of fatalities.

The main toxic outcome is the disruption of nerve cell functioning that can lead to cardiac arrest and respiratory depression. This however needs dosage in excess of 300ml for the toxic effects to be felt. The reason for high toxicity in orally ingested essential oils is that it gets quickly and completely absorbed by the body. 

Dermal essential oils toxicity can occur when high concentrations of these oils are administered to the skin. Sometimes, this can lead to liver and kidney damage. Since both these organs are essential, especially to filter out toxic substances, damage to them can be fatal. 

Chronic toxicity

Repeated use of essential oils over many months or even years can produce adverse skin reactions and other health problems. Some common symptoms of chronic essential oils toxicity are nausea, headaches, lethargy and minor skin irritations.

toxic effects of essential oils

Toxicity depends on the dose and major risk is posed by taking these essential oils internally. If they are being administered orally, care must be taken to give the correct dose especially where babes and children are concerned. In countries like the UK, only external administration of these oils is legally permitted. Since oral administration poses the greatest risk, this should only be taken under medical supervision. 


When UV rays combine with phototoxic oils, a photochemical reaction can take place. The result could vary in degrees from a mild color change to the skin to extreme tanning and hyper-pigmentation. In extreme cases of phototoxicity, deep burns and blisters can occur. Some of the essential oils that can cause phototoxicity are -lemon, bergamot, bitter orange, grapefruit and lime.

The reason why such oils are risky is that part of the chemical composition is removed – E.g. Bergamot. This risk can be minimized or even eliminated if the following precautions are followed:

  • Distil citrus oils
  • Get bergamot that is free of furanocoumarin
  • If you do use phototoxic oils, ensure that you do not expose the treated areas to strong light or sunlight for at least 8 hours.

Other reasons for toxicity can be because users are unaware how to use them properly:

  • Accidental ingestion by adults and children
  • Women using them for abortion
  • Suicide attempts
  • Children being given essential oils by parents
  • Clients being prescribed these oils by ill-trained therapists

If adults or children accidentally or deliberately ingest essential oils, they must be rushed to the nearest hospital for emergency care. 

Why is toxicity associated with essential oils?

Utilizing low doses of essential oils for holistic aromatherapy treatment is considered quite safe. In many western countries, especially in the UK, only external low-dose aromatherapy massages are used as a form of beauty therapy. High-doses and internal applications are not allowed. In France however, higher doses are used both internally and topically and this is dose-dependent. Hence, French aromatherapists have greater understanding of essential oils toxicity, contra-indications and safe dosage levels.

Experts suggest that essential oils be used only after practitioners gain full knowledge. One of the main problems of toxicity is the lack of a keen understanding of the oils being used and their side effects. This is why there is such fear in certain quarters about the dangers of using essential oils even for therapeutic purposes.

Another reason for toxicity of these oils is that books written for the layman are being used by professional aromatherapists too. Instead, professional practitioners must have comprehensive knowledge that goes beyond using aromatherapy as a ‘fad’ beauty treatment. High standards of training and practice of aromatherapy have to be introduced similar to medical herabilsm. 

List of a few toxic essential oils

Oils that should be completely avoided due to their toxicity are – almond (bitter), aniseed, arnica, boldo, calamus, camphor, cassia, horseradish, mugwort, mustard, pennyroyal, rue, sassafras, savin, tansy, thuja, wintergreen, wormwood and wormseed.

The following are some of the oils that are not banned but must be used with care. These recommendations come from IFRA (International Fragrance Association) and they include – angelica, bitter orange, bergamot, cassia, cinnamon bark, cumin, grapefruit, lemon, lime, tagetes, oak moss, pinaceae, rue, verbena, tree moss. 


It is best that aromatherapy and prescribing essential oils for oral intake is undertaken by trained practitioners. There have been no severe cases of essential oils toxicity when it is used within a limited dosage of 100mg to 300mg / day. Topical applications of essential oils in aromatherapy also do not pose major health problems as long as the medical condition of the client is studied thoroughly before any form of administration.