"So how exactly do you make an aromatherapy blend?" Honestly, creating an aromatherapy blend is part science and part art. It is science in the sense that you are looking for oils that will have a specific effect on the body or mind. If a client is looking for a blend that will help them prevent muscle soreness after a workout, you wouldn't give them a blend that contained oils that have very little known action on the muscles; rather, you would create something that combines oils that are known to help alleviate soreness, as well as increase circulation and warm the area. Blending is art in the sense that you have to know which scents will go well together. There are some who would argue that all scents go well together and that you can put almost any oils in a blend. This may be true in some cases, but I find blends are almost always more pleasant when the combined scents are at least relatively similar in character. So, for instance, I would try to avoid combining sweet orange oil with pine. There's nothing particularly wrong with that combination, and depending on the therapeutic application, it may be entirely appropriate, but if you are looking to create something that works well therapeutically and smells good, that may not be the best combination to choose. Rather, since both these oils are known to uplift the mood, I would choose either another uplifting citrus or a gentle floral or herb to go with the sweet orange, or another conifer or herb to go with the pine.
Now that we've established the basics of how a blend is created, we'll dive in a little deeper. Let's say that I have a client (we'll use the example mentioned above) who is something of a "weekend warrior," and who always finds that their muscles are incredibly sore after a workout. This is especially noticed in their legs, since the majority of their weekend activity involves hiking or something similar. As an aromatherapist, I will first consider oils that directly treat the physical ailment. Since the client is not asking for something to uplift their mood or give them fortitude to complete a workout or go back to work after a long weekend, I will not be as concerned with the mental and emotional effects of the oils I select. Thus, I would pick some combination of the following oils: birch, lavender, rosemary, spearmint, peppermint, black pepper, and cypress. All of these oils have properties that would encourage muscles put through a strenuous workout to heal. Birch has high concentrations of methyl salicylate, which is the primary ingredient found in such preparations as Bengay; lavender is renowned for its external and internal healing properties and is one of the most versatile oils; rosemary increases circulation and helps tone muscles; spearmint and peppermint, especially in combination with birch, will warm the muscles and increase circulation, providing that well-known cool-to-warm sensation that liniments give when they are applied; black pepper warms and tones the muscles as well as increasing circulation; and cypress tones the blood vessels and increases circulation.
However, would I put all of these oils into a single blend? The general rule is that a blend is best when it contains no more than five essential oils. Otherwise, you may end up with a blend that is actually less effective than intended. So, to narrow down the oils I have selected as starters, I will think again about the physical complaint, which is intense soreness after a workout. This intense soreness will require oils that have more of an affinity for treating that particular ailment. Therefore, I would choose birch, spearmint, peppermint, and black pepper to provide a blend that acts as a liniment to both prevent overwhelmingly sore muscles and treat any soreness that does occur. Alternatively, if two types of mint seem like too much for the blend, rosemary could be substituted for the spearmint. This will depend partly on the preferences of the client. If they don't want something that smells quite as minty, then the rosemary would be a good choice. Also note that I have selected essential oils that, overall, have scents that are quite compatible with one another, each one having a warming, invigorating quality.
We've selected the oils to use in the final blend for the client. The next step is choosing the proper concentration for the blend, which involves adding the essential oils together and then diluting them down with a carrier oil such as sweet almond, jojoba, or grapeseed. I traditionally make my blends in the 2.5%-5% dilution range, since that is ideal for most therapeutic applications. In infants, young children, or people with sensitivities, a lower dilution would be necessary; for spot-treatment of an area or for short-term intense therapy, a higher concentration may be necessary. For this particular blend, I would choose a slightly higher concentration, simply because it would be for short-term treatment of acute symptoms. I would most likely choose a 20% or 30% dilution, which is concentrated enough to act as a liniment without being so powerful as to cause skin irritation. A patch test would still be advisable to ensure no allergic reaction to any of the oils.
Once a dilution has been chosen, it's time to add each of the essential oils together. But how do I choose how much of each essential oil to add to the blend? Each oil has something called a "blending factor," which is essentially how potent of a scent the oil has. The blending factors are based on a scale of 1-10, with 1 being most potent and 10 being least. For the oils in this blend, birch has a blending factor of 1-2, peppermint of 1-2, spearmint of 2-3, and black pepper of 3-4. As you can see, the blending factor is not a "hard and fast" measurement of an oil's potency, as the potency can itself rely on factors such as the region in which a plant was grown, the method by which it was harvested, etc. Since these oils all have similar blending factors, they can be mixed in roughly similar ratios. If they had blending factors that were significantly different (such as a 2 versus a 5), then I would add more of the less potent oils to the blend. As I would be looking for a more liniment-like blend for this client, I would choose to add slightly more of the birch and mints to the blend than the black pepper. This is especially true since the birch and mint are the core of the blend, whereas the black pepper is a supporting oil.
Another factor to consider when making a blend is how the client will be applying it. In this case, since this blend would act as a liniment, I would recommend that the client soak in a hot bath as soon as they are able to after their weekend workout and stay in there for as long as they comfortably can. This will start the therapeutic action on the legs which the liniment will continue. Nice, warm, blood-infused skin and muscles will be better permeated by the oil blend, which the client would apply via gentle massage immediately after they exit the bath and dry off their legs. I would also be wise to inform them, especially if they've never had a liniment before or are unfamiliar with the actions of birch and mints on the body, that they should expect to feel as though their legs are both freezing and on fire at the same time for a little while after applying the liniment. This would eventually subside into a pleasant warmness, supplemented by the warming qualities of the mints and the black pepper.
All of this, then, is what goes into making an aromatherapy blend. As you see, it can be a complex process, depending on the blend required; and it involves keeping in mind the necessary actions of the blend, its desired potency and effect, and its method of application. Sound knowledge of the oils being used, as well as the intuition to be able to blend them pleasantly, are key in creating blends that are therapeutic to both body and mind.