Returning to the safety theme, grouping essential oils. By any standards the commonly used essential oils are very safe however knowledge and caution should be used for certain oils. Some oils should only be used under the guidance of a properly trained aromatherapist.
140 ESSENTIAL OILS A to D E to J L to N O to S T to Z
origins and allergens notes for Shirley Price college oils
In 1993 a guide was published that grouped the 140 oils obtained by distillation and 9 by expression.
Group 1 the safest category contains 65 essential oils all having oral and dermal toxicity at or above 350mls per 70kg adult. Thats a lot of essential oil! Oils should not be taken internally as all oils irritate mucous membranes. These oils were tested at concentration of 12-30% on human volunteers without any irriatation or sensitisation reactions. Generally it is recommended to use 15 drops in 50ml of carrier oil for massage.
Group 2 has the same oral toxicity as Group 1 but higher dermal toxicity. 10 essential oils.
Group 3 contains the citrus oils. 9 essential oils. Their extraction by expression means they can contain some non volatile components which render some of them phototoxic (not to be used before going into sunlight). Because they are produced by expression (squeezing the rinds) we favour the use of organically certified citrus oils to avoid pesticide residues.
Group 4-7,these are 33 essential oils with increasing degrees of oral toxicity but the same low dermal toxicity.
Of these Group 7 oils have oral toxicity of 0.5g/kg to 1.5g/kg. Group 7 oils include Basil and Hyssop (which itself should be used only by professional aromatherapists).
So it can be concluded that all these 117 oils could be used safely in a 2% skincare cream though Basil and Hyssop should be avoided.
Higher risk oils possess certain hazards and caution in their use is recommended expressly by using in more dilute fashion.
Thuja, recommended dilution limit 2%
Citronella, Tagetes dilution limit 0.25-1% and avoid for hypersensitive individuals
Cinnamon Bark dilution limit 1% but this oil has the possibility of strong sensitisation so should always be used by first making a patch test 24 hours before use.
Caraway, Cumin Oil, Clove leaf oil have moderate to high dermal toxicity, Clove leaf contains 95% eugenol. Oregano, Savory. recommended dilution limit 2%
Clove leaf's toxicity is 1.37g/kg so for a 70kg adult thats about 100g while essential oil is commonly supplied in 3ml to 10ml bottles.(clove bud which is used by aromatherapists has lower toxicity)
this excellent guide can be obtained second hand.