So what's up with using essential oils on horses? First let's see what people are saying. Check out this 2 minute video. Hmmm. Sounds pretty unbelievable to me. We're going to need some more research here. Let's dive into the history of medicinal plants and aromatherapy.
Way back in the day, pre-medieval scholars started to believe that plant oils had healing properties. Not having any real medicine, they were pretty desperate for anything that might help combat infection and disease. They had limited success; some plant oils were mildly antiseptic, and smearing them over a wound could help keep it clean. (Honey and rendered animal fat were also used for this purpose.) Some plants had active healing powers, like willow bark, which acted as low-grade asprin. None of these home remedies were as effective as modern drugs, but they were (sometimes) better than nothing.
As ideas about medicine progressed, healers came to believe that scent was important in curing disease too, making nicely scented oils even more valuable. During the era of the Black Plague, many people believed that carrying around sweet-smelling flowers would help drive away sickness. No one yet understood how germs worked, so "bad air" was blamed for carrying disease. This idea continued into the Victorian period, where proper ventilation and fresh air, clean were considered extremely important for health.
“All smell is, if it be intense, immediate acute disease; and eventually we may say that, by depressing the system and rendering it susceptible to the action of other causes, all smell is disease.”
--Edwin Chadwick’s Report on the Sanitary Condition of the Labouring Population of Great Britain 1842
Eventually humanity developed real science, and the idea of smells as disease-carriers and healing tools dropped by the wayside. Then we skip forward a bunch of decades, and the 60s, 70s and 80s happened. All of a sudden ancient stuff was way groovy again. Crystal healing, astrology, incense, nature-worship and aromatherapy/essential oils came back into popularity. By this time though, believers had dropped the "scent can carry disease" angle and focused just on the good stuff.
The idea of "natural remedies" became very appealing. I can see why. No one likes going to doctors; they are expensive, poke you in awkward places, and hand you prescriptions for medicine you don't really understand. Natural remedies, however, give a patient a feeling of being in control again. They're usually easy to understand, you don't need permission to use them, and they don't often have side-effects. Plus, they sound appealing. Just based off of their names, would you rather take Geldanamycin or lavender? Well obviously lavender. But do nice-smelling oils work?
Mostly...not. No. Sorry. There is next to zero evidence that essential oils or aromatherapy have any measurable benefit in treating or preventing illnesses in humans or animals. Ditto for most other types of alternative medicine. Yes, there are some "studies" out there that say differently, but those "studies" are largely unscientific and conducted by the same folks selling what they're "testing."
BUT WAIT. We do know that the placebo effect sort of works! The placebo effect is basically Dumbo's "Magic" feather. Dumbo didn't need it to fly, but it boosted his willpower and confidence, enabling him to get airborn. Study after study has shown us that sugar pills given to patients convinced they were real medicine were pretty effective. Surprisingly, human willpower is one of the best tools in overcoming illness! This is probably why alternative medicines seem to work for some folks. The power of prayer, meditation, fasting, sweat lodges, and yes, essential oils, derives from our own willpower. Pretty cool, eh? The human mind is a miracle. We convince ourselves better.*
So case closed, right? Essential oils must be A-okay. Uhhhm, WAIT. Unfortunately, the world is full of malicious bullshitters trying to screw folks over. Remember how the lady in the video claimed that the horse could be treated for "negative emotions" by rubbing oil on his ears? Yeah, that's the crap I'm talking about. Some peddlers of essential oils will try to convince you that their products can help cure anything, and so of course you should buy as much as possible. Check out this Facebook advertisement for Equine Raindrop Therapy (click to enlarge):
Holy CRAP, they're claiming oils can treat everything from cancer to strangles!! Oils can treat aging, pain, laminitis, spinal problems, depression, viruses, ringworm... everything!
It's the fucking fountain of youth over here!
It's Magic!! Expensive magic.
How much is a "Raindrop" treatment kit? $164!!
And about 1/10th of an oz of a single oil can cost over $50!!
A single day of learning about the power of oils costs $175!! (That's $21/hour for an 8 hour day.)
Holy fucking shit, if I had no morals, I'd be an animal psychic and an oil peddler. Cha-CHING$$!
Listen up folks. There's a fine line between "do whatever makes you happy" and being an idiot.
Horses don't benefit from the placebo effect like humans do. You can't convince them a medicine works, so they won't convince themselves that it works. The most that will happen is that you become convinced the oils work, so you're calmer, so your horse is calmer too. Fine and dandy. BUT...
Besides not actually fighting cancer or strangles, essential oils can be dangerous. They can provoke allergic reactions, cause skin to become more light-sensitive and, when used frequently, even damage the liver. Essential oils that aren't organic can contain concentrated pesticides. Many people mistakenly use essential oils directly on skin, when they should be diluted with "carrier" oils. Not diluting them can cause serious skin problems.
And the $164 you could spend on "Raindrop Therapy," couldn't you use that to better effect? Instead of rubbing your horse's ears with peppermint, how about hiring a professional saddle fitter? What about getting radiographs of your horse's hooves, so your farrier can see exactly what he's working with? What about simple crap like sunscreen, flyspray, vitamin supplements, a new winter blanket, better fencing? How about a session with a trainer? And what about vaccines, worming, etc? I sure as hell hope you're not skipping out on actually essential vet care to pay for shellacking your horse's face with rosemary. But some people really do skip out on actual medical care in favor of faith healing-- sometimes even when it comes to their own children. Just check out this terrible story.
The moral of the story here folks is that there's nothing exactly wrong with oiling up your horses... just don't depend on it to actually accomplish anything.
You can read more about quack science medicines for horses here.
*By the way, the opposite is true too-- humans can convince themselves sick. Hypochondriacs actually do experience weird symptoms. And crowds of humans can convince each other that a "mystery illness" is spreading-- these people experience symptoms even though nothing is medically wrong with them. It's called psychosomatic mass hysteria, and it's more common than you might think.