Chemical Families

Knowing essential oil chemistry opens up an entirely new world of blending possibilities. Often, aromatherapists and aromatherapy educators use essential oil chemistry as a starting point when looking to formulate a blend for a specific therapeutic intention. Lemon essential oil, for example, is far more than just an oil that smells divine. It is also rich in the chemical component limonene (d), a member of the monoterpene family, which helps cleanse, disinfect, and purify. The beautiful thing about looking at chemical components is that there is a wealth of research on these components and their effects. This adds even more credibility to the reasons why lemon essential oil is a perfect choice for a DIY surface cleaner recipe. The science behind essentials oils and aromatherapy adds confidence and clarity to the discussion of how essential oils can help promote a healthy, holistic lifestyle.


  • Effective antifungal properties— blend with a soothing oil such as Sandalwood or Lavender
  • Anti-inflammatory
  • Antispasmodic
  • Antibacterial
  • Serves as a tonic/sedative to the nervous system
  • Cooling

Safety: Oils with a significant aldehyde content can irritate the skin. If oxidized the damage can increase considerably. Citral, a main component in these oils, is irritating to the skin surface and the mucous membranes. Using low concentrations of aldehydes in blends is generally safe for the skin. Use 5-6 drops of aldehyde high oils per ounce of a carrier and combine with oils high in monoterpenols. Aldehydes are very susceptible to oxidation, so keep in an airtight bottle and store in a cool, dark place. People with estrogen-related cancers should avoid the internal use and high-dose, long-term skin use of oils high in citral. In such cases, you can use high-citral oils in 1% dilutions for short periods without concern.


  • Antispasmodic— ranging from a gentle antispasmodic action to a powerful one, depending on the oil. Many aromatherapists consider the component, isobutyl angelate (found in Roman Chamomile), as one of the best antispasmodics available.
  • Can have pronounced sedative effects.
  • Balancing and soothing— esters are known as the “balancing components”. Many esters have significant regulating and rebalancing effects on the sympathetic nervous system. Oils high in esters are often emotionally uplifting.
  • Some are analgesics, such as Inula, Jasmine, Lavender, Roman Chamomile, and Ylang Ylang.
  • Some are useful digestive aids, such as Cardamom, Roman Chamomile, and Bergamot.
  • Generally anti-inflammatory and effective in soothing skin rashes and skin irritations.
  • Adaptogenic— helps the body adjust to and deal with stress.

Safety: With proper dilutions for applying to the skin, there are generally no safety concerns. The only exception is the component, methyl salicylate, which can cause skin and eye irritation, among other things. (Methyl salicylate is present in Wintergreen.)


  • Antispasmodic
  • Can help maintain healthy intestinal flora, especially when there is gas pain
  • Promotes healthy digestion

Safety: Take care with skin application as these oils can irritate the skin. Essential oils with a high content of ethers can raise toxicity concerns when used in larger doses. Use these oils in low doses (less than 1% in a blend) and only for acute, short-term use. Avoid using oils with ethers during pregnancy. Oils high in ethers should never be used long-term. (Examples of oils high in ethers are Aniseed and Sweet Fennel.)


  • Essential oils (such as Rosemary ct camphor, Spike Lavender, and Peppermint) that contain a significant percentage of ketones are valuable for respiratory infections, as they tend to have highly effective mucolytic and expectorant properties.
  • Oils with high ketone levels can have analgesic tendencies.
  • Menthone (found in Peppermint) has carminative effects.
  • Some oils high in ketones may help with a scar and wound healing, such as Spike Lavender and Vetiver.
  • Peppermint, Rosemary ct camphor, and Spike Lavender can have circulatory effects.

Safety: All ketones do not have the same safety concern or therapeutic behaviors, so you have to consider each component individually. The following are non-toxic ketone compounds: menthone, verbenone, vetivone, fenchone, carvone, piperitone, jasmone, and turmerone. Aromatics International does not sell the oils that have ketones with serious toxicity concerns. However, camphor content (such as in Rosemary and Spike Lavender) can cause concerns for some. Avoid using oils with camphor for those who are epileptic, pregnant, or have a high fever. Do not place preparations with camphor into or near the noses of infants and young children. If ingested by infants or children, camphor can prove fatal. Camphor can cause convulsions either from oral ingestion or, more rarely, inhalation. Camphor can also cause miscarriage, but only in almost fatal doses. (Lethal dose is only four teaspoons!) Only use oils that contain camphor for short periods of time and in small amounts. A general rule is to use only 1% of ketones in a 1-ounce blend. Additionally, ketones are resistant to being metabolized by the liver and can tend to accumulate, so there is some concern when using ketones in high daily doses over long periods of time. Those with liver diseases should only use minimal amounts of oils high in ketones. Although camphor is a CNS stimulant, overdoses can cause CNS depression.


  • Mild antiseptic properties.
  • Useful decongestant properties for the respiratory and the muscular system.
  • The rubefacient effect provides circulation and pain relief for muscle pain and stiffness.
  • Some monoterpene oils are anti-inflammatory.
  • Mild antibacterial effect— some may even be antiviral.
  • Highly lipophilic— penetrates the tissues of the body easily (penetration enhancers).
  • Effective airborne deodorizers and purifiers.
  • Improves general health.

Safety: Oils high in monoterpenes can cause skin irritation or sensitization if they have oxidized. It is essential to store them tightly closed in a cool, dark place. Monoterpenes are not water-soluble; avoid in the bathtub unless they are well diluted in a carrier oil. Studies have shown that the monoterpene, limonene, is a potential irritant and allergen when oxidized.


  • Essential oils containing a significant percentage of alcohols are often powerful anti-infectious agents because they have antibacterial, antifungal, and sometimes antiviral activity.
  • Non-toxic and mild on the skin and mucous membranes.
  • They are great for long-term support for the immune system.
  • Research has shown that linalool (linalol) is effective against bacteria and geraniol is effective against fungi. The research also suggests that terpinen-4-ol in Tea Tree oil activates white blood cells that deal with infections.
  • The specific components of menthol, linalool (linalol), alpha-terpineol, and geraniol make the site of an application feel cold and provide local anesthetic effect. Linalool (linalol) offers a significant sedating quality, making oils such as Lavender or Rosewood ideal for use in your insomnia blends.
  • Oils high in Monoterpenols are useful in skin care as they provide antiseptic and sometimes anti-inflammatory properties and are generally safe and healing for the skin.
  • Can act as a tonic for the nervous system.
  • Supports emotional balance.
  • Can nourish and strengthen the immune system by detoxifying.
  • Blends that contain Geranium, Lavender or Bergamot have a natural deodorizing effect as these oils help to inhibit bacteria.
  • Monoterpenol high oils have antispasmodic qualities for soothing muscles, especially the specific components of geraniol, linalool (linalol), menthol, citronellol, and borneol.

Safety: Most monoterpenol rich oils are generally safe on the skin and are not known to irritate. One exception is peppermint, which can potentially be a skin irritant. Do not use menthol-rich oils on children under five years of age. It is also harmful if inhaled by infants. Anyone advised to avoid antimalarials, sulfonamides, chloramphenicol, streptomycin, or aspirin should avoid menthol-rich oils. Geraniol (found in Palmarosa, Geranium, Citronella, Rose, Fingerroot, and Thyme ct. geraniol) may cause mild skin sensitization. Do not exceed a dermal maximum of 5.3%. Robert Tisserand states that many studies show that linalool (linalol) is incapable of eliciting any allergic reactions in a healthy person. It has an extremely low risk and demonstrates broad-spectrum anticancer activity in cell lines.


  • Oils high in oxides are potentially very powerful aids in any respiratory illness.
  • Essential oils containing significant amounts of 1,8-cineole (except German Chamomile) have antiviral, antifungal, and antibacterial effects.
  • 1,8-cineole is a stimulant for the glands of the respiratory system. It is expectorant and mucolytic, stimulating mucus-secreting cells and activating the cilia of the respiratory mucous membranes.
  • 1,8-cineole has a stimulating effect on the mental process, increasing blood flow to the brain when inhaled.
  • Research has shown 1,8-cineole has an anti-inflammatory effect on bronchial asthma, decreasing coughing, shortness of breath, and can ease expectoration.
  • 1,8-cineole is a skin penetration enhancer. It is also has a drying effect.
  • 1,8-cineole is an analgesic and anti-inflammatory agent for muscular and respiratory systems.
  • The oxides in German Chamomile offer muscular decongestion and anti-inflammatory effects.

Safety: Take care when using 1,8-cineole with asthmatics, as it is possible to set off an attack. An asthmatic attack is an individual response to the oil, dosage, application, and specific situation. Do not use with infants. Take care when using for children under the age of 10. If oxidized, it can cause skin irritation and sensitization.


  • Essential oils containing a significant percentage of phenols are highly anti-infectious agents that are for use in acute situations. (Use oils high in monoterpenols for long-term infections.)
  • Rubefacient— increases local blood circulation, causes minor skin irritation, vasodilation, and local analgesic effect.
  • Can have anti-inflammatory effects when used with other skin healing oils in a blend.
  • Used in acute illnesses and infections to stimulate the immune system.

Safety: Oils high in Phenols are the most irritating oils to the skin and mucous membranes and can cause dermatitis and sensitization. If phenols are present in high concentrations in an essential oil, use that essential oil in very low dilutions on the skin and for short periods of time. They are generally not safe for the skin in a bath. Use in small amounts when blending oils for diffusing. (No more than 10% of the blend!) Do not use oils high in phenols with babies and children. Do not use Clove oil with people who have clotting disorders, as it is high in the phenolic component eugenol, which is an anticoagulant.


  • With sesquiterpenes, you should consider the therapeutic effects of each oil individually, as one cannot generalize these components as easily as with most other chemical families.
  • Oils high in sesquiterpenes can have anti-inflammatory, antibacterial, antiseptic, analgesic, and antispasmodic properties.
  • Even a small amount of sesquiterpenes in a carrier oil can have a pronounced therapeutic effect.

Safety: Oils high in sesquiterpenes do not generally have safety concerns. Although, Black Pepper may cause irritation for those with sensitive skin, and some additional sesquiterpenols may become skin irritating if oxidized. According to Tisserand, b-elemene found in Myrrh has shown antiangiogenic action, meaning it suppresses new blood vessels from forming. This may help with preventing tumor growth. However, it may also suppress fetal growth and best avoided during pregnancy.


  • The therapeutic properties of sesquiterpenols can vary greatly, as the individual components have unique effects.
  • Many oils high in sesquiterpenols have grounding, antispasmodic, antibacterial, skin healing, and anti-inflammatory effects.
  • Some of the oils offer long-term support for the terrain (entire body and all that goes into keeping it healthy), can act as tonics for the veins and lymph system and are immune stimulants.

Safety: Sesquiterpenols are generally safe oils and are not known to irritate skin. If you use anticoagulant drugs, have peptic ulcers, or have any bleeding disorders, avoid oils that contain b-eudesmol, such as Blue Cypress. Additionally, some sesquiterpenols can have an antiangiogenic effect, which means it suppresses new blood vessels from forming. Do not use during pregnancy.