Essential oils often evoke thoughts of scented candles and day spas, but their benefits beyond relaxation are less well-known. Essential oils are ultimately just plant extracts—and those are used in countless cleaning and personal-care products, and are the main ingredient in some pest-control products and some over-the-counter medications, like Vick’s VapoRub and some lice sprays. They’re used in the food industry because of their preservative potency against food-borne pathogens—thanks to their antimicrobial, antibacterial, and antifungal properties. Various oils have also been shown to effectively treat a wide range of common health issues such as nausea and migraines, and a rapidly growing body of research is finding that they are powerful enough to kill human cancer cells of the breast, colon, mouth, skin, and more.

A handful of promising, real-life studies have been conducted with humans and other animals, though most of the research in that realm thus far has been conducted in the lab. More controlled trials will be required before some of these applications  will be available to the public, but meanwhile, scientists have turned up exciting results in another area of use: countering the growing antibiotic-resistance crisis. “The loss of antibiotics due to antimicrobial resistance is potentially one of the most important challenges the medical and animal-health communities will face in the 21st century,” says Dr. Cyril Gay, the senior national program leader at the United States Department of Agriculture’s (USDA) Agricultural Research Service.

As Cari Romm previously reported in The Atlantic, livestock consume up to 80 percent of the antibiotics used in the U.S., and the amount actually jumped by 16 percent between 2009 and 2012, according to a recent FDA report. This rampant use of the drugs has led to “superbugs” that are becoming increasingly resistant to the antibiotics that are used to treat not just farm animals, but humans as well. In fact, almost 70 percent of the antibiotics given to these animals are classified as “medically important” for humans. According to Romm, “In the U.S., antibiotic resistance caused more than two million illnesses in 2013, according to a report by the Centers for Disease Control and Prevention, and an estimated 23,000 deaths,” and they’ve also amounted to an extra $20 billion in healthcare costs. And it’s only poised to get worse: a recent report commissioned by the U.K. government estimates that drug-resistant microbes could cause more than 10 million deaths and cost the global economy $100 trillion by the year 2050.

While the drugs are, of course, sometimes necessary to treat infections in livestock, the real reasons they’re overused are to speed up growth and to compensate for the cramped, unsanitary living conditions the animals endure. Dr. Stuart B. Levy, a man of many titles—hematologist and professor at Tufts University; director of the Center for Adaptation, Genetics, and Drug Resistance; president of the Alliance for the Prudent Use of Antibiotics; and author of the book The Antibiotic Paradox: How the Misuse of Antibiotics Destroys Their Curative Powers—says he and his colleagues consider the misuse of antibiotics on farms to be the biggest influence on antibiotic resistance, which has been declared “an increasingly serious threat to global public health that requires action across all government sectors and society” by the World Health Organization. Levy has been warning about this impending disaster for nearly 40 years, a couple of decades after farmers discovered that putting small amounts of antibiotics in the animals’ feed resulted in increased growth. Even back then, a study led by Levy found that chickens developed resistance to the antibiotic tetracycline at a rapid pace–within a week, the animals had resistant bacteria in their gut. Months later, the stubborn bugs had spread to untreated chickens and even the farmers. And it didn’t stop there: Those resistant bacteria also became resistant to other antibiotics that the chickens hadn’t even consumed. “Antibiotics used anywhere creates antibiotic resistance, and that resistance doesn’t stay in that environment,” Levy says. “And resistance is transferrable among bacteria of different types.”

What’s being done to confront this major contributor to this obvious, growing world health threat? The FDA has asked those in the agricultural industry to voluntarily reduce their use of antibiotics, but no one is keeping track of whether they do (nor has there been a record of the antibiotic use all these decades). Farmers can still say they’re using it for prevention of infections. “The lobby is so strong it’s hard to get categorical refusal to do this,” Levy says. “We really want to convince the users—the farmers—that this is a practice that should be eliminated.”

Whether farmers choose to use it or not, there is a strong alternative on the horizon. Numerous recent studies—including several done by the USDA—have shown great promise in using essential oils as an alternative to antibiotics in livestock. One of their studies, published in October 2014 in the journal Poultry Science, found that chickens who consumed feed with added oregano oil had a 59 percent lower mortality rate due to ascites, a common infection in poultry, than untreated chickens. Other research, from a 2011 issue of BMC Proceedings, showed that adding a combination of plant extracts—from oregano, cinnamon, and chili peppers—actually changed the gene expression of treated chickens, resulting in weight gain as well as protection against an injected intestinal infection. A 2010 study from Poultry Science produced similar findings with the use of extracts from turmeric, chili pepper, and shiitake mushrooms. A multi-year study is currently underway at the USDA that includes investigations into the use of citrus peels and essential oils as drug alternatives.

Researchers have also directly compared the effects of commonly used antibiotics with those of various essential oils. One such study, from the March 2012 issue of the Journal of Animal Science, found that rosemary and oregano oils resulted in the same amount of growth in chickens as the antibiotic avilamycin, and that the oils killed bacteria, too. Additional findings have shown that essential oils help reduce salmonella in chickens, and another study found that a blend of several oils can limit the spread of salmonella among animals. One of the co-authors of that study, Dr. Charles Hofacre, a professor at the University of Georgia’s College of Veterinary Medicine, says it’s such a new area of research that they don’t yet know exactly how the essential oils work, but “there is some strong evidence that they are functioning by both an antibacterial action in the intestine and also some have an effect to stimulate the intestinal cells ability to recover from disease more quickly–either by local immunity or helping keep the intestinal cells themselves healthier.”

Lavender (Florin Gorgan/Flickr)

Of course, there is also a dire need for alternatives to antibiotics for the direct treatment of infections in humans and animals, not only for illness prevention and growth-boosting in livestock. Research investigating the use of essential oils in humans has produced encouraging results, but such studies have been small and surprisingly rare, especially given the demonstrated success of their use in livestock. An Italian study found that a combination of thyme and clove essential oils was just as effective in treating bacterial vaginosis as the usual antibiotic treatment, and results of a study by U.S. researchers show that staph-infected wounds healed faster when they were treated with vapors of tea-tree oil than with conventional methods. Research published in December 2013 reported that a hand gel made with lemongrass oil was effective in reducing MRSA on the skin of human volunteers, and previous research has shown that a cleanser made with tea-tree oil clears MRSA from the skin as effectively as the standard treatments to which bacteria appear to be developing resistance. This type of simple, inexpensive fix—an essential-oil-based hand sanitizer—could be a major boost to hospitals, in particular, since MRSA infections are so common in healthcare settings.

In the lab, scientists have been testing all kinds of combinations of essential oils and antibiotics, and they’re repeatedly finding that the oils—used on their own and in combination with some common antibiotics—can fight numerous pathogens, including antibiotic-resistant strains of E. coli, Staphylococcus aureus (which causes staph infection), and other common types of bacteria. Results consistently show that combining essential oils and antibiotics significantly lowers the amount of antibiotic required to do the job. For example, two recent studies showed that lavender and cinnamon essential oils killed E. coli, and when combined with the antibiotic piperacillin, the oils reversed the resistance of the E. coli bacteria to the antibiotic. Another recent study found that basil oil and rosemary oil were both effective in inhibiting the growth of 60 strains of E. coli retrieved from hospital patients. Other research has produced similar results for many other essential oils, both alone and in combination with antibiotics. Researchers believe that one mechanism by which the oils work is by weakening the cell wall of resistant bacteria, thereby damaging or killing the cells while also allowing the antibiotic in.

Further investigation is clearly needed to advance this promising area of research, but that would require time and money. “Such investment is not likely to come from the mainstream pharmaceutical industry, which has not placed much emphasis on antibiotic development for a number of reasons, including the excessive cost in bringing a single drug to market without a commensurate return,” says Dr. Nicole M. Parrish, associate professor of pathology at the Johns Hopkins University School of Medicine and associate director of medical mycobacteriology at The Johns Hopkins Hospital, who co-authored a recent review on the potential use of essential oils as alternatives or supplements to antibiotics.

She says the situation is urgent: When she and her colleagues perform testing to determine the appropriate medication for a patient, they often find that there are no longer any effective antibiotics in existence to treat the bacteria in question. “We feel helpless in the face of this growing threat, and the answer as to why we have not made more progress on this front is simple: economics.  Unfortunately, the 'specter' of monetary gain overshadows the perspective from 'the trenches.'” She says that essential oils contain some of the most potent antimicrobial compounds available, and that furthering our understanding of them may lead to the development of entirely new classes of drugs. “Let us all hope the prevailing wind changes to move this field of research forward,” she says.

Gay explains that “phytonutrients” or “phytochemicals” are chemical compounds derived from plants that have a range of health benefits, “including promoting tumor killing and increased resistance to infectious diseases, and they have been used as health-promoting agents by many cultures for several millennia.” Their potency isn’t surprising when you consider that the plant compounds that make up essential oils exist in the first place to help plants protect themselves from infection, endure temperature variations, heal from damage, and repel pests. Still, skepticism is likely in a culture like ours that is used to lab-created synthetic medicines (not to mention the bad reputation essential oils may have gained from being frequently touted as miracle cures for everything), even though some of our most important and common pharmaceuticals originated from plants. For example, aspirin is derived from willow bark, though the key compound is now synthesized by manufacturers; the treatment for malaria (still used today) is derived from fever-tree bark; morphine is derived from the poppy plant; the cancer-fighting drug paclitaxel was initially derived from the bark of the Pacific yew tree; and many cold and cough medicines and muscle-relief creams have mint extract as the main ingredient. Even a newly developed Ebola treatment hinges on the use of tobacco plants.

Back on the farms, some are already putting essential oils into practice. “There are a number of companies that are currently selling plant extracts as feed additive, and large integrated producers are also adding feed additives to their rations to enhance the health of animals, especially their intestinal health, during their production cycle,” Gay says. No one seems willing to readily offer that information, though—and they don’t have to. One farmer who has talked publicly about using essential oils is Scott Sechler, owner of Bell & Evans Farms, a high-end producer of antibiotic-free poultry. Back in 2012, he told the New York Times about his use of oregano oil and cinnamon to fight infection on his farms, which now number about 140 with a total of 9 million chickens at any given time. Though he says the approach worked better than all other options he had tried, he still told the Times, “I have worried a bit about how I’m going to sound talking about this,” adding, “But I really do think we’re on to something here.” He clearly knows about the stigma attached to his approach, despite the fact that it’s working. So,essential oils are truly a secret weapon, an unsung hero being used successfully but not quite openly.

Cinnamon (Dennis Brekke/Flickr)

It took Sechler nearly 10 years just to get the people he works with to believe in his method, including farmers, workers at the feed mills, and his own employees, of which there are now around 1,200. He has met his share of skepticism from colleagues, too. For someone who notes that he lacks a formal education, Sechler is at the forefront of some cutting-edge methods (for one, he counts Temple Grandin, the famous animal-science expert, as a friend who helped him implement a humane slaughter system). He has been on the antibiotic-free kick for about 30 years, and he describes his current method in terms of its effects on gut bacteria—another hot topic right now. “We started with a breed of chicken that wasn’t raised to be stressed and overfed and to live in sanitary conditions,” he says. They also feed the chickens high-quality grains enhanced with essential oils, and they avoid the use of toxic chemicals like hexane, which is commonly used by other farmers in processing their feed. “With our chicken breed, housing environment, and feeding program, we’re able to promote healthy gut bacteria—we use oregano oil to kill the bad bacteria and cinnamon oil to support the good bacteria.”

He says his model works for him because he’s not trying to correct a problem that’s already out of control. Some farmers need more powerful weapons because they’re trying to compensate for ongoing problems caused by improper cleaning practices and unsanitary living conditions. They might put baby chickens on the remnants of manure from previous flocks because they don’t properly clean out the barn first, and then they may use chlorine to wash the processed chickens. Whatever bacteria (and antibiotics) that aren’t left at the chicken plant end up on plates. On Sechler’s farms, he says he doesn’t allow these problems to get out of hand in the first place. “You can’t just introduce essential oils into a bad environment and expect magic–—they don’t fix a screw-up,” he says. “But if you meet them halfway by doing things right, they will carry you across the finish line.” People warned him that the bacteria would become resistant to the essential oils, too, but they haven’t yet, and his farms processed over 50 million chickens last year. According to C. Norman Shealy, a Duke-educated neurosurgeon and author of The Healing Remedies Sourcebook: Over 1000 Natural Remedies to Prevent and Cure Common Ailments, it is possible for bacteria to become resistant to essential oils, but it’s unlikely because the oils contain hundreds more chemical compounds than antibiotic medications, making it difficult for bacteria to adapt to the oils.

Adopting healthier practices may cost a penny or nickel more per pound, which could affect stock prices of the big poultry producers. Sechler, whose company is not publicly traded, says he has been fortunate to have a loyal and ever-growing customer base that is willing to pay a bit more for better quality. Sechler says if the public starts asking for antibiotic-free meat en masse, more producers will comply, and change should come from other key players, too. “Essential-oil use by the food industry should be a hundred times bigger than it is,” he says. “Universities need to be able to speak up to some in the industry without getting their heads chopped off,” instead of tiptoeing around them because they provide research funding. He also believes the USDA and the FDA should create standards limiting antibiotic use and require everyone in the industry to comply by a certain date, similar to the way fuel efficiency standards for cars have been introduced and enforced.

“Unfortunately in this industry, you have to force people. Unless everyone has to do it, many won’t,” Sechler says. Despite encouraging study results and Sechler’s proven success, the lack of regulation and record-keeping is a potential problem with the use of essential oils, too: “These products are being used every day, but I really can’t tell you how many chickens or turkeys are being given these products because I don’t think there is anyone keeping track of this across the country,” Hofacre says, and Gay notes that the feed additives are not regulated either. “However, they are being used very successfully and I think as we learn more about the various essential oils and other plant extracts we will find more effective combinations,” Hofacre says.

Levy thinks the investigations into plant extracts as alternatives to antibiotics is “wonderful,” but he cautions that for any alternative, “it should be demonstrated that this practice is really useful, and alternatives should be given the same scrutiny” that antibiotics haven’t been.