Chemical Families, Therapeutic Properties, and Safety Considerations

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Chemical Families, Therapeutic Properties, and Safety Considerations

The components that essential oils are made up of are classified into chemical families according to their molecular structure. Knowing the chemical families and their therapeutic properties can really help us learn which essential oils to use for various health concerns. There are also safety concerns within each family that are to be taken into consideration as selections are made. Here is a brief summary of the different chemical families, the therapeutic properties, and any safety concerns. Keep in mind that essential oils are complex, individually, and may or may not follow along 100% with the chemical family guidelines.


This chemical family is made up of components which evaporate quickly and are considered “top notes” as they are the first aromas to hit your nose in a blend.

Monoterpenes generally are:

  • antiseptic – great for cuts
  • analgesic – relieves pain
  • rubifacient – increases blood circulation
  • decongestant – relieves respiratory congestion
  • antibacterial (some also antiviral)
  • excellent for diffusing – they kill airborne germs
  • skin penetration-enhancers – great for getting deep into sore muscles, tendons, and ligaments

Essential oils with more than 60% monoterpenes include: Bergamot, Black Pepper, Cypress, Frankincense, Grapefruit, Juniper Berry, Lemon, Opopanax, Sweet Orange, Ravintsara, Rosemary, and Siberian Fir.

Safety Considerations: Monoterpenes are prone to oxidation and have a shelf life of only 1-3 years. Once oxidized, they can cause skin irritation, and are best discarded (or diffused).


This chemical family’s therapeutic properties are difficult to generalize. Here are some therapeutic actions and the Sesquiterpene-family essential oils associated with them:

Anti-fungal: Myrrh, Patchouli, Spikenard
Analgesic: Black Pepper, German Chamomile, Ginger, Myrrh, Ylang Ylang
Antiseptic: Cedarwood, Ginger, Myrrh, Vetiver
Anti-inflammatory: Cedarwood, German Chamomile, Ginger, Myrrh, Patchouli, Spikenard, Ylang Ylang
Antispasmodic: German Chamomile, Ginger, Opopanax, Spikenard
Sedative: German Chamomile, Myrrh, Patchouli, Spikenard, Ylang Ylang

There are really no safety concerns with Sesquiterpenes other than they can be irritating if oxidized. They have a long shelf life of 6-8 years.


The chemical structure of Monoterpenols are similar to that of Monoterpenes. The difference? A hydroxyl molecule. The location of this molecule determines the therapeutic property of the oil (isn’t that fascinating?).

Monoterpenols have a wide variety of therapeutic properties. Some of these often include:

  • strong anti-infectious agents, such as terpinene-4-ol, a chemical component found in Tea Tree
  • antibacterial, antifungal, and even antiviral, thanks to linalol, a chemical component found in Lavender and Rosewood
  • anti-spasmodic effects thanks to menthol, a primary component found in Peppermint
  • anti-fungal action found in Geranium

Some of the essential oils highest in Monoterpenols are: Rose Absolute (93%), Rosewood (91%), Palmarosa (80%), Thyme ct linalol (61%), and Basil (56%).

The only safety consideration in this chemical family is menthol, which can irritate the skin. Menthol should be avoided on children under 5 years of age. Shelf life is 3-5 years.


The oils in this chemical family are considered “base” notes, as they are physically heavier on a molecular level, and are the last notes to float out of a bottle when you are sniffing a blend. Sandalwood is 85% sesquiterpenols.

General therapeutic properties of Sesquiterpenols are:

  • anti-inflammatory
  • immune supporting
  • sedative
  • skin healing
  • antibacterial
  • antispasmodic
  • excellent tonic for lymph system as well as veins

There are no safety concerns with these oils. Shelf life is 6-8 years.


This chemical family is not only highly antispasmodic, but are also often:

  • sedative
  • soothing
  • analgesic
  • anti-inflammatory
  • and helps the body deal with stress

Some of the essential oils with the highest percentages of esters are Roman Chamomile (80%), Jasmine Absolute (52%), and Helichrysum (49%).

Esters are generally free from concern, with proper dilution. There are only two components that are best avoided: methyl salicylate present in Birch and Wintergreen, and sabinyl acetate present in Juniper oil. Methyl salicylate can be poisonous if used long-term on the skin, and sabinyl acetate can cause liver toxicity. Shelf life is 3-5 years.


Phenols are very active and stimulating – an excellent choice when you want to nip an aggressive infection in the bud.

Clove Bud essential oil is 67% Phenols and is the “poster child” of Phenols. Excellent for combating infections, but should be avoided by people on blood thinners due to its high eugenol content.

Base notes, Phenols sticking around longer and making them more apt to irritate the skin. When using high-Phenol oils, dilute well. Use no more than 5 drops per ounce of carrier oil (1% dilution), to prevent irritation on mucous membranes and skin.

Shelf life is 3 years.


Aldehydes are excellent for fungal issues. Melissa, and it’s near-twin, Lemongrass, are two oils right around 80% Aldehydes. Neral and geranial are two specific Aldehydes Melissa and Lemongrass share.

Aldehydes usually have the following therapeutic properties:

  • anti-fungal
  • antibacterial
  • anti-inflammatory
  • antispasmodic
  • sedative
  • and can even reduce fever.

This is another chemical family where low dilution and short-term use is strongly recommended. Dilutions over 1% can result in skin irritation. Aldehydes are most definitely not recommended for internal use ever, even at low doses. People suffering with glaucoma or estrogen-related cancers should be particularly cautious.

Aldehydes oxidize easily and have a shelf life of only 1-3 years.


The primary reason to choose oils from the Ketone chemical family would be for respiratory infections, as they are very effective expectorants and mycolytics. Peppermint has more ketones than most other essential oils, although Rosemary, Vetiver, and Spike Lavender have an effective amount as well.

Ketones are also generally:

  • analgesic
  • antispasmodic
  • rubifacient
  • cicatrisant
  • wound healing

Although Ketones do have components which are non-toxic, there are very real concerns with camphor in particular.

Pinocamphone and isopinocamphone are also neurotoxic, and these components are found in Hyssop (Hyssop officianalis).

Also found in Hyssop (Hyssop officianalis), as well as Sage, Mugwort, Thuja, and Pennyroyal are pulegone and thujone, potential abortifacients. Do not use if pregnant or around children.

Short-term use of low dilutions (1%) is considered safe. Shelf life is 3-5 years.


The most important Oxide component is 1,8 cineole, which is wonderful for respiratory issues. 1,8 cineole stimulates mucous and activates the cilia found in the mucous membranes.

Other therapeutic properties of Oxides generally are:

  • antiviral
  • anti-fungal
  • antibacterial
  • can stimulate blood flow to the brain when inhaled

Eucalyptus is your best choice for an Oxide high essential oil, as it contains around 80% Oxides. Rosemary and Laurel Leaf contain around 40% Oxides and are also good choices.

Although Oxides can provide relief to asthmatics, in some people it can set off an attack, and caution must be given. Other safety concerns are skin irritation due to oxidation of oils.

Oxides should be avoided on children under the age of 10. Shelf life is 1-3 years.


Ethers have very effective antispasmodic properties.

Some popular ethers are: Anise, Fennel, Nutmeg, and Tarragon.

Safety considerations for the Ether chemical family are high, so these are to be used preferably only when Esters don’t work. These safety considerations are: liver toxicity, estrogen-like activity, neurotoxic effects, are psychotropic (influences mood and behavior, as well as affects the brain), and genotoxicity (interferes with DNA).

Specific Ether components and the safety concerns they present are as follows:

  • Apiole – oral doses are poisonous, and can cause an abortion in pregnant women.|
  • Methyl chavicol (estragole) – carcinogenic in rats, likely to cause cancer in humans. High percentages of estragole are found in Tarragon, Hzvozo Bark, and Tropical Basil.
  • Methyl eugenol – high doses are carcinogenic.
  • Trans-anethole – Avoid if pregnant or breastfeeding. This component is found in high concentrations in Anise and Fennel essential oils.

Of all chemical families, Ethers present the most serious safety issues. This is concerning because many people see the names of herbs, such as Fennel, Basil, and Nutmeg and are less concerned with dosage due to their familiarity and often frequent use of these herbs.

Excerpt taken from the e-report, Using Essential Oils Safely. FREE when you sign up for our newsletter here.

Lea Harris is a Certified Aromatherapist with Advanced Graduate training from Aromahead Institute in July 2013, but she is not a doctor. Please consult a trained aromatherapist or your doctor before using any of the suggestions on this website, as the user's age and health conditions must be taken into account before using. The information contained in this website is for informational purposes only, and should not be used as a substitute for professional medical advice.


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