When administered for internal use, essential oils, like herbal remedies, are more often used in combination rather than singly. The idea behind this is both to increase their efficacy and tailor their use to the needs of a particular client’s condition. All three of the world’s major traditional medical systems (Chinese, Greek and Ayurvedic medicine) have developed the fine clinical art of combining single remedies to create formulas. These traditional systems of herbal medicine all began with simple, tried and tested herb clusters that later became the building blocks for more complex, comprehensive formulas. Over millennia, physicians wrote hundreds of texts (known as formularies) containing formulas for treating particular syndromes and disorders. We can do the same when using an essential oil to treat physiological conditions. There exist only two types of combinations among remedies: synergistic and complementary.
Keep in mind that combinations suggested in this text are meant as examples only – although they are important examples in themselves. By no means exhaustive, they are given here as a stimulus to further clinical experimentation. After all, the clinical reality here is the client’s treatment needs: this is what finally determines specific oil selection.
Synergistic combinations
Combining two or more essential oils with the same properties will create a synergistic effect that mutually enhances the strength and effectiveness of a particular action. For instance, Lavender and Clary sage, when combined, create a greater particular action than when either is used separately. Specifically, pairing these two oils produces a stronger nervous restorative and nervous relaxant action than otherwise possible with either one alone. Another example would be the synergistic action achieved by combining Marjoram and Peppermint. Together, their spasmolytic and analgesic action (particularly on the gut) is superior than if either is used alone.
Despite the empirically proven effectiveness of this type of remedy combining in clinical practice, we are justified in asking about any science behind this principle. Taking recourse in the oils’ chemical constituents, we find that a synergistic action is usually obtained when the dominant constituents are the same. In the case of Lavender and Clary sage, it could be argued that the synergy lies in the simple meshing of esters with esters. Taking this example to the next level of secondary constituents, we again find monoterpenols fusing and therefore presumably mutually enhancing their effect. In the second example of Marjoram and Peppermint, the dominant constituents are monoterpenols; the synergistic action is achieved presumably through the fusion of both similar and dissimilar types of monoterpenols. Conceivably the presence of both types of monoterpenols would strengthen and enrich their bonding. Of these two oils’ secondary constituents, we find a significant proportion of monoterpenes in both, which would only add to the overall ability of these two oils to form a new functional unit. Clearly, both these oil pairs are therefore good examples of very effective synergistic combinations.
Other good examples of good synergistic oil pairing would be Tea tree and Thyme ct. linalool for an enhanced antifungal action, where various monoterpenols reinforce each other; Niaouli and Ravintsara for an enhanced antiviral action (especially with acute respiratory infections), where 1,8 cineole and various monoterpenes would work in tandem; and Black spruce and Scotch pine for a stronger neuroendocrine restorative action, involving the synergy of various monoterpenes.
The other way to arrive at synergistic combinations, and without knowledge of the oils’ chemistry, would be to use the empirical method of the energetic fragrance qualities. Lavender and Clary sage, for example, are both essentially green oils and therefore are potentially relaxing and cooling – which implies usage in hypertonic/ tense and sthenic/hot conditions respectively. While it is true that these functions have the advantage of being holistic – that is, affecting both mind and body as one – they are very broad descriptions that lack the precision of chemical pharmacology when it comes to understanding or at least rationalizing known physiological actions and combinations. On balance, the clinical model of the fragrance categories is more useful when the focus is comprehensive body-mind rebalancing rather than specific
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physiological intervention. Ultimately, both potentially contribute hugely to our understanding of how essential oils work in clinical practice.
Complementary combinations
Combining two or more essential oils with different properties will create a complementary effect where one oil is supported with an assistant oil of a different character or quality to reinforce a particular action. Rather than creating a single synergistic action as discussed above, here two oils can enhance each other by combining different actions. Lavender and Marjoram, for instance, make for a good complementary combination that targets hypertonic/tense neuromuscular conditions. Both oils act as relaxants but possess different energetic qualities and constituents. Lavender is a sweet-green aromatic dominated by esters, while Marjoram is a pungent- herbaceous green oil dominated by monoterpenols and monoterpenes. The combination of their complemetary qualities and constituents makes their particular relaxant action more comprehensive and focused, and therefore clinically more effective for treating painful spasmodic conditions of the heart, coronary circulation and digestive tract.
Another example would be the complementary effect achieved by combining Marjoram with Blue tansy in treating asthmatic conditions. Both oils are systemic nervous relaxants with good bronchodilatant (bronchospasmolytic) and analgesic actions. However, while Marjoram is also a particularly effective smooth- and striated- muscle relaxant that opens the chest and relieves wheezing, Blue tansy is additionally a strong anti-inflammatory and antihistamine oil that will address the inflammatory component of asthma. Here, their common relaxant action on bronchial smooth muscle is enhanced by their other focus of action, effectively resulting in a more comprehensive treatment of asthmatic conditions.
Good complementary oil combinations usually involve two dominant constituents that are different and yet achieve the same therapeutic effect. In the case of Lavender and Marjoram, the action of Lavender’s esters is presumably assisted by the action of Marjoram’s monoterpenols. In the example of Marjoram and Blue tansy, the complementary effect of monoterpenols is supported by sesquiterpenes. Again, the fact that both oils also contain significant amounts of monoterpenes strengthens their general affinity through a minor synergy and ultimately encourages positive clinical results.
Anther example of a good complementary combination is Tea tree and Niaouli, two Melaleuca species that together create a broad anti-infective action for treating a wide range of infections. Here the monoterpenols of sweet Tea tree are complemented by the 1,8 cineole of fresh-pungent Niaouli. Both oils also share significant levels of monoterpenes that serve to reinforce their complementary action with a secondary synergistic one.
Blue tansy and Helichrysum make a good complementary pair in the treatment of immediate allergies through their shared anti-inflammatory and antihistamine actions.
Blue tansy’s sesquiterpenes (notably azulene) match Helichrysum’s esters and ketones. For the treatment of venous congestion in the lower limbs causing varicose veins, Patchouli’s sweet-woody sesquiterpenols and sesquiterpenes are complemented by the floral-sweet monoterpenols of Geranium.
How can one uncover complementary combinations where one fragrance quality is supported by another possessing the same function? In the complementary combination of Lavender and Lemongrass, for instance, we find a green oil supported by a lemony oil for treating inflammation and fever. Both aromatic qualities potentially have cooling effects. The energetic functions of Lavender and Lemongrass, therefore, are described as ‘clearing heat,’ through the combined energies of the green and lemony fragrance quality. The function of ‘clearing heat’ has wide implications on the whole body-mind-emotions system and implies heat on the mental-emotional level as well as the physiological one. In terms of their constituents, sweet-green esters and monoterpenols (Lavender) are assisted by lemony monoterpenic aldehydes (the citral, geranial, etc. in Lemongrass) to create anti-inflammatory and antipyretic actions. This particular case clearly illustrates a direct dovetailing between the empirical energetic and the pharmacological approach to oil combining. However, it is generally best to support any conclusion drawn with rationales based on oil constituents that match their larger energetic fragrance character.