Chemistry
1- Acids – anti-inflammatory
Acids are remarkably powerful anti-inflammatory. Even if found only as a trace element, they remain very active. Acids are very soluble in water. Acids are rare substance, we only find them in trace elements.
Therapeutic properties:
- powerful anti-inflammatory even in small doses
- antalgic
- hypotensor (relaxing power helps with the release of tension)
- anti-spasmodic
Usage: soothes many rheumatic ailments
Dangers and counter-indications :
Certain plants such as gaultheria can provoke a poisoning effect because of their strong content of salicylates and methyl.
EO rich in acids must be handled very cautiously and in very small quantities.
People allergic to aspirin must abstain from the use of EO that contain acids, especially salicylic acid.
Examples of acids: cinnamic acid, salicylic acid, benzoic acid, lemon acid, myrtenic acid
Some EO that contain acids: Sandalwood – Yellow birch – Gaultheria – Common juniper – Clove – Vetiver
2- ALCOHOLS and PHENOLS
Alcohols are a generic term that includes phenols, monoterpenoids, sesquiterpenoids and diterpenoids, that are almost the most abundant molecules in the chemical composition of EO. These are more or less effective anti-infectious and act either by neutralising the pathogenic germs or alternatively, directly by rebalancing it. They also have an immune-stimulant and a neuro-tonic action. They are recommended in all cases of microbial, bacterial, viral and fungal pathologies. Their toxicity varies depending on their biochemical family.
Physical action: viral fungal anti-infection (in-depth treatment)
Psychological action: balance and serenity
PHENOLS
They are the powerful anti-infectious of the world of essences that kill germs directly by destroying their cellular membrane. Phenols EO can be recognised by their often sharp fragrance, reminiscent of the odour of a disinfectant.
Therapeutic properties:
- Powerful anti-infectious (short treatment), notably the most powerful anti-bacterial. These are remarkable fungicides, virucides and skin or intestinal anti-parasites
- Phenols stimulate immune defences and blood irrigation. By their heating activity and their overall tonic power, the EO belonging to this chemical group succeed in dissolving cramps and fortifying nerves.
- Immuno-stimulants, they increase blood pressure but can be the cause of cardiac arrhythmia if abused.
Specific therapeutic properties : Eugenol : antispasmodic.
Usage: respiratory infections, bacterial and viral, urinary tract and vaginal infections, internal and external mycoses (candida for example), intestinal parasites of all types.
Dangers and counter-indications
- Dermo-caustic if used pure on skin and mucous
- Usage in very small doses and dilution of 5% in a VO in the case of skin or oral application
- Delicate to use and one needs to respect absolutely the warnings and usage precautions as well as the recommended doses.
- Not recommended to very reactive and sensitive people
- Beware! Take great care if the liver is fragile
- Forbidden for pregnant women, children under the age of 7 and epileptics.
Good to know: it is strongly advised to alternate the use of phenol-based oils with oils rich in terpenic alcohol that are easier to use.
Examples of phenols: Thymol : Thyme CT thymol (Thymus vulgaris CT thymol) ; Carvacrol : Origan compact (Origanum compactum), wild savory (Satureja montana), Eugenol : Clove (Eugenia caryophyllus), Ceylonese cinnamon(Cinnamomum verum) ; Chavicol : exotic basil (Ocimum basilicum) ;
A few EO that contain phenols: Ajowan, St Thomas berry, Ceylonese cinnamon, Clove, Oregano, wild savory, thyme with Thymol…
MONOTERPENOID ALCOHOLS or monoterpenic alcohols
Much gentler action than phenols and these can be used in long-term treatments, with the only exception of EO containing menthol.
Therapeutic properties:
- General and nervous system tonics
- Broad spectrum anti-infectious, antiviral, anti-parasite
- Bactericide et fungicide
- Friend of the skin
- Stimulates the immune system
Specific therapeutic properties: Thujanol-4: liver stimulant, Menthol: liver stimulant, vasoconstrictor, Alpha terpineol: soothing
Dangers and counter-indications : none
- They can be applied without causing any skin irritation, even pure on a small surface. They are recommended for the treatment of children and older people
- Not recommended for pregnant women (first three months of pregnancy).
Examples of Monoterpenoids: geraniol, linalool, thujanol, menthol, borneol, alpha-terpineol, terpinene-1-4-ol
Some EO that contain monoterpenoids: Sweet basil with linalool, Rosewood…
« SESQUITERPENOIDS » ALCOHOLS (or sesquiterpenic alcohols)
Therapeutic properties:
- Acts on the circulatory systems (venal and lymphatic decongestant).
- Immuno-modulating and immuno-stimulating, even is very small doses. They are equalizers that, because of their oestrogen-like qualities help also to regulate the female hormonal system.
These alcohols are rather different from their monoterpenoid friends.
Their anti-infectious properties are weak.
Specific therapeutic properties:
carotol stimulates hepatic regeneration cultivated Carrot (Daucus carota)
spathunelol has an antifungal action ( Lemon verbena.)
Viridiflorol: oestrogen-like*, phlebo-tonic Niaouli (Melaleuca quinquenervia)
Cedrol: phlebo-tonic Provence cypress (Cupressus sempervirens)
santalol: general tonifying action (cardio-tonic) white sandalwood (Santalum album)
Beware of « hormone-like » action of certain alcohols such as viridiflorol
Dangers and counter-indications: None except the properties of viridiflorol
.Examples of sesquiterpenoids (or sesquiterpenic alcohols): viridiflorol (beware, oestrogen-like), cedrol, spathulenol, santalol, carotol
Some EO that contain sesquiterpenoids: Carrot, Encense, Patchouli, lentisque Pistachio, Sandalwood, Vetiver, Ylang-ylang…
Dangers and counter-indications: terpenic alcohols, monoterpenoids or sesquiterpenoids and diterpenols do not present any toxicity when used at the preconised dosage. They can even be used pure on the skin.
Beware! Some sesquiterpenoids are known to have hormone-like effects. One needs, therefore, to remain vigilant and always check the counter-indications of essential oils.
The best-known alcohols
Alpha-terpineol: Ravintsara (Cinnamomum camphora CT cineole), Eucalyptus radiata (Eucalyptus radiata), Niaouli (Melaleuca quinquenervia)
Bisabolol: German camomile (Matricaria recutita)
Citronnellol: Geranium rosat (Pelargonium x asperum)
Farnesol: Roman camomile (Chamaemelum nobile)
Geraniol: Palmarosa (Cymbopogon martinii),
Lavandulol: True lavender (Lavandula augustifolia)
Linalol: Rosewood (Aniba rosaedora), Thyme CT linolol (Thymus vulgaris CT Linalol), Ho wood (Cinnamomum camphora CT linolol)
Menthol: Peppermint (Mentha X piperata), Wild mint (Mentha arvensis)
Nerolidol: Neroli (Citrus aurantinum flower)
Terpinene-1-ol-4 : Tea-tree (Melaleuca alternifolia), organic Marjoram (Origanum majorana)
Thujanol: Thyme CT thujanol (Thymus vulgaris CT thujanol), organic Marjoram (Origanum majorana), garden Marjoram (Origanum majorana CT thujanol)
8- Lactones
Lactones are most often trace elements in EO, which therefore limits its toxicity. They have the same properties as the ketones but are more powerful.
Physical action:
- mucolytic and expectorant
- anti-infectious (antibacterial and antifungal)
- anti-coagulant and antispasmodic
.Usage: pathologies that produce mucus (chronic bronchitis or spasmodic bronchitis).
Dangers and counter-indications:
Neurotoxic, abortive, allergenic.
Forbidden for pregnant and breastfeeding women, children under the age of 10, elderly people with a fragile nervous system.
Toxicity: same neuro-toxicity found in ketones if they are taken in large doses.
.Examples: alantolactone, santalolactone, artemisinin (anti-malaria), alpha-santonine (acaricide, ematicide), massoialactone, xanthine, nepetalactone
Some EO containing lactones: Yarrow, Roman chamomile, fragrant inula, Italian Helichrysum – noble Laurel
Ketones – Powerful expectorant
Ketones are very active molecules that become rapidly toxic. Therefore they should be used with caution and discernment. They are very interesting therapeutically in the regeneration and healing of tissues and the elimination of haematoma.
Psychological action (calming, sedative)
Physical action (mucolytic, healing)
Therapeutic properties:
- Expectorants and decongestant of the bronchial system.
- Liquefy mucous (mucolytic), fats (lipolytic) and blood
- Cleansing: elimination of fats and allowing a decongestant effect on the liver
- Anti-inflammatory, skin healing and regenerating, antiparasitic
Anti-haematoma properties. Italian Helichrysum is the best representative of all ketonic EO. Its characteristics of acting fast and ridding the body of haematoma (even on babies and toddlers – by cutaneous path.)
Monoterpenic ketones are healing, regenerating, lipolytic, mucolytic, coagulators and anti-infectious.
Sesquiterpenic ketones: mucolytic, powerful fungicides, regenerating and healing for the skin.
Diterpenic ketones: have the same properties with, in addition, a powerful ability for anticoagulation and anti-haematoma.
Dangers et counter-indications:
-Neurotoxic and abortive (always favour cutaneous path when possible)
-No diffusion
-Toxicity: ketones are difficult to use because of their inversion effect. In weak doses they have a negative effect, are calming and sedative. When the dosage is increased, or when doses are repeated, they become neurotoxic and can provoke epileptic fits.
Totally forbidden for women who are pregnant or breastfeeding, children under the age of ten and older people whose nervous system is weak. In all cases, you should consult an aromatherapist.
Be particularly attentive to the cumulative effects of long-term treatments or high doses
The oral administration of EO containing ketones must be carried out with great care, in preference under the informed eye of a medical practitioner or a specialised therapist.
Examples of ketones: Atlantone, beta-dione (anti-haematoma!), borneone (=camphor), carvone, cryptone, fenchone, Italdione, menthone, pinocarvone, pinocamphone, piperitone, Pulegone, tagetone, thujone, verbenone, vetivone
A few EO containing ketones: Atlas Cedar – Eucalyptus globulus- Lemon Eucalyptus – Italian Helichrysum – Peppermint – Myrrh – Rosemary CT camphor – Rosemary CT verbenone – Sage Officinalis – Vetiver
EO containing monoterpenic ketones: Eucalyptus globulus, Hyssop officinalis, stoechade Lavender, Green Mint, Camphor Rosemary, Verbenone Rosemary, Sage
EO containing sesquiterpenic and diterpenic ketones: Cedar, Curcuma, Helicrysum, Myrrh, Manuka, Vetiver.
Terpenes
Terpenes are the most common molecules in essential oils. These are hydrocarbons that are produced by many plants, especially conifers.
Suffix in -ENE
The most frequent molecules. The majority of terpenes procure a positive effect and stimulate.
Physical action: venous and lymphatic decongestant
Psychological action: meditation and anchoring
There are several subclasses:
MONOTERPENES – decongestant
Physical action: respiratory and lymphatic decongestant, aerial antiseptic, immuno-stimulant, antibacterial
Psychological action: strength and courage
Therapeutic properties:
- tonic properties, general stimulant. Clears the respiratory tract
- decongestant of the venous system, the respiratory and lymphatic systems and tonifies blood circulation
- digestive stimulant, limonene, zinziberene…
- hormone-like properties. Useful for stimulating the adrenals and balance the thyroid…
- anti-infectious properties. Especially in atmospheric diffusion (as in pine forests).
- immunostimulant
Monoterpene examples: alpha-pinene, beta-pinene, camphene, carvene, limonene, terpinene (alpha, beta), …

Some EO that contain monoterpenes: Frankincense, Black spruce, Juniper, Niaouli, Sweet orange, Oregano, Grapefruit, Rosemary verbena, Rosemary camphor…
- from delta-3-carene: leaves and branches from cypress
- with alpha-pinene: plants with needles
- from limomene: citrus zest
- from paracymene: analgesic percutaneous present in plants with thymol and carvacrol (thyme and savory).

Dangers and counter-indications:
- Dermo-caustic
- Dilute at least at 50 % in a good VO for all skin applications.
- Often used in diffusion, they are very effective as antiseptic. Limonene is found in most citrus. These are analgesic and stimulate the immune system.
The particular case of monoterpene cortisone-like: alpha et beta-pinenes (Sylvester pine et Black spruce)
SESQUITERPENES
Sesquiterpenes are substances that appear, in minimal concentration, at the end of EO distillations that have a long duration (such as roots, and wood resins).
Their action spectrum is very broad. They generally have a gentle action and are well-tolerated overall.
Therapeutic properties:
- Hypotensor, soothing and sedative.
- Anti-allergic (ex: chamazulene), anti-inflammatory (ex: germacrene) and analgesic.
- Decongestant effect and lymphatic system drainer
- They are also antiseptic, bactericide, analgesic and spasmolytic. In some cases, they stimulate the liver, the spleen and the pancreas. They are also excellent immuno-stimulants.

Dangers and counter-indications: Contrary to the monoterpenes, they are better tolerated by the skin and do not provoke skin irritation. The sesquiterpenes EO must not be mixed with ketones.

Some EO that contain sesquiterpenes and azulenes: Sandalwood, Atlas Cedarwood, Himalayan Cedarwood, Frankincense, Myrrh, Patchouli, Vetiver, Ylang-ylang…
- Cedrene: atlas cedarwood
- Beta-caryophyllene: Lamiaceae
- Chamazulene: german chamomile
- Farnesene: ylang-ylang
- Alpha and Beta himachalene: atlas cedarwood
- Cadinene, Selinene, Viriflorene, Zingiberene…
