How can you recognise a potentially dangerous essential oil in aromatherapy?

There is one essential thing to know: an essential oil is a concentrated and complex liquid extract of an aromatic plant, obtained by steam distillation of aromatic plants or parts of these plants (flowers, leaves, wood, roots, bark, fruit, etc.). It is the distilled essence of the aromatic plant. As a result, essential oils contain concentrated active molecules, some of which pose a potential danger that you should be aware of.

What are the dangers of the main essential oils?

There are many essential oils, and they contain substances that can be dangerous if not used correctly or on the “right people”. An active substance is a chemical component with specific biological effects that may also have toxic potential. This toxicity is not uniform and can vary depending on several factors, including the biochemical composition of the substance, the dose administered, the route of administration, and the physiological state of the exposed individual.

Types of toxicity in essential oils	Main compounds involved	Examples of essential oils	Main risks	Major precautions
Dermocaustic (irritant/skin burns)	Phenols (thymol, carvacrol, eugenol)	Thyme ct thymol, savory, compact oregano, clove	Burns, severe skin irritation	Always dilute heavily, avoid applying undiluted and to mucous membranes
Dermocaustic (irritant/skin burns)	Aromatic aldehydes (cinnamaldehyde)	Cinnamon (leaves, bark)	Severe irritation of skin and mucous membranes	Strict dilution, avoid sensitive areas
Dermocaustic (irritant/skin burns)	Terpenic aldehydes (citrals, citronellal)	Verbena, lemon eucalyptus, lemongrass, lemon litsea, lemon balm	Moderate skin irritation, irritation of mucous membranes	Systematic dilution, avoid mucous membranes and fragile skin
Skin irritant	Monoterpenes (pinene)	Pines, firs	Possible irritation	Dilute for local applications, avoid sensitive areas
Photosensitising	Furocoumarins	Citrus zest (lemon, orange, grapefruit, mandarin), bergamot, angelica, khella, cumin	Burns, pigmentation spots after UV exposure	No sun/UV exposure for at least 6 hours after application or oral intake
Allergenic	Sesquiterpene lactones	Laurel, annual mugwort, sweet inula	Allergic skin reactions	Always perform a skin test beforehand; avoid use in individuals with known allergies
Neurotoxic / Abortive	Ketones (thujone, pulegone, italidione, menthone, piperitone, verbenone, etc.)	Helichrysum, peppermint, sage, camphor rosemary, Atlas cedar	Risk of convulsions, neurological toxicity, risk of miscarriage	Contraindicated in pregnant/breastfeeding women, infants and children under 6 years of age, epileptics, elderly people; avoid oral administration
Hepatotoxic	Phenols (thymol, carvacrol, eugenol)	Thyme ct thymol, savory, compact oregano, clove (oral use)	Hepatic toxicity in case of overdose or prolonged treatment	Limit to 1 drop 3×/day, max 500 mg/day and 3 weeks; combine with a hepatoprotective essential oil if necessary (carrot, thyme thujanol, lemon, rosemary verbenone)
Nephrotoxic	Monoterpenes	Pine, fir, juniper, sandalwood, cypress	Renal toxicity in case of prolonged oral use	Avoid long-term oral treatment; caution in patients with renal insufficiency
Nephrotoxic Skin irritant	Pinene (monoterpenes)	Scots pine, lemon tree, balsam fir, black spruce, juniper	Long-term renal risk, skin irritation	Avoid prolonged oral use, always dilute for topical application

Always adjust the dose, route of administration and duration, and seek advice from a healthcare professional trained in aromatherapy, especially for children, pregnant women and frail individuals.

What precautions should be taken to avoid the dangers of essential oils?

It is essential to take several precautions when using essential oils to avoid injury or health problems , which can sometimes be serious.

General precautions

• Never inject essential oils.
• It is strongly advised not to use essential oils on pregnant women, during breastfeeding, or on children under 3 years of age.
• It is imperative not to leave bottles of essential oils within reach of children. Store them carefully, preferably upright.
• Avoid using pure essential oils, with exceptions such as true lavender, ravintsara, rosewood, etc.
• Never apply pure essential oil to the eyes or mucous membranes.
• Avoid using essential oils directly in bath water.
• Do not expose essential oils to sunlight, as some of them have different properties and therefore specific effects and may be phototoxic.
• If you are prone to allergies, perform a skin test on the inside of your elbow and wait approximately 15 minutes to observe any reaction.
• Before use, be sure to check the appropriate method of administration and dosage for each variety of essential oil.

What to do in case of an accident?

• If an excessive amount of essential oil is accidentally ingested, it is imperative to contact the poison control centre immediately . In the event of accidental ingestion of excessive amounts of essential oil, take approximately 30 ml of vegetable oil to dilute the substance and minimise the associated risks .
• If an essential oil comes into contact with the eyes or causes skin burns, immediately apply a vegetable oil, such as sweet almond oil, to dilute and reduce the irritating effect.

Storage of essential oils

• Keep essential oil bottles out of the reach of children. Store them carefully, preferably in an upright position.
• Store them away from light, preferably in a coloured or aluminium bottle inside a cupboard.
• Maintain the storage temperature between 5 and 35 degrees Celsius maximum.
• Observe the shelf life, which is generally 5 years for essential oils and 3 years for essences.

These precautions apply to all essential oils. However, some have specific contraindications, so consult a healthcare professional for advice.

FAQ – Potentially dangerous essential oils