Drugs 2.0

"Essential oils" sounds like a spa treatment, but could they help in the battle against drug-resistant bacteria?

February 27, 2015

Charles Hofacre’s office used to smell like pizza, which is pretty strange since he works in chicken research. The culprit was a huge tub of oregano oil that he kept near his desk. Instead of pouring the oil on a slice of Sicilian, however, Hofacre fed it to the birds.

A veterinarian at University of Georgia’s Poultry Diagnostic and Research Center, Hofacre is helping companies try to find an alternative to antibiotics that farmers can give to livestock. Antibiotics prevent poultry from contracting a low-level intestinal disease that keeps the fowl from converting grain to muscle. If the birds stay healthy, they fatten up faster. Hofacre receives formulations of essential oils—defined as concentrated liquid from a plant—from a variety of companies and tests them to see how good they are at killing bacteria. That pizzalicious day he was looking at oregano oil; tomorrow it could be eucalyptus. 

Photo: ItineranttraderA vial of lavender essential oil

Right now 80 percent of the antibiotics sold in the United States are administered to livestock—mostly to promote growth and prevent disease in overcrowded conditions. This practice is helping to breed antibiotic-resistant bacteria that can diminish the efficacy of life-saving drugs. It’s a very, very serious problem. But if essential oils can kill bacteria and fight off diseases, they could lessen demand for antibiotics, which might help keep those medicines working.

The Centers for Disease Control and Prevention stated in 2013 that we may soon run out of antibiotics that can effectively treat disease, thanks to the drugs’ overuse in the medical and agricultural industries. Drug-resistant bacteria on food animals can transfer to the people who handle them. They can also contaminate meat. Just one month after the CDC’s report, a salmonella outbreak traced back to the California-based poultry company Foster Farms sickened 634 people. The salmonella strain in many of those cases was immune to antibiotics.

“We got complacent,” says Nicole Parrish, a pathologist at Johns Hopkins Medical Center. In the past, she explains, we had so many antibiotics in our arsenal that simply modifying the synthetic drugs already in use could do the trick. Now, as superbugs become more prevalent, we have to rely on nature.

Hofacre calls essential oils “a really new area for us, to understand how to control diseases without having to use antibiotics.” People have been concocting “natural remedies” out of lavender, eucalyptus, or orange extracts for centuries, but they did so with little, if any, scientific understanding of why those medicines seemed to work. So Hofacre, Parrish, and others have begun to tease apart those age-old oils in the search for something new.

Parish and microbiologist Stefan Riedel, also at Johns Hopkins, think something in the oils might weaken bacterial cell walls or prevent the walls from forming altogether. Essential oils, they say, may become their own suite of agents with antimicrobial or antibacterial properties one day, diversifying the tools we keep in our medicine cabinets.

Todd Callaway, a microbiologist from the USDA, is looking into cow and sheep guts. He worked with Phillip Crandall, a food scientist at the University of Arkansas, and found that feeding orange rind to cattle and sheep significantly reduced the amount of salmonella and E. coli bacteria in the animals' digestive systems. 

The body of research on plant-derived oils’ agricultural impact is growing—there’s this paper, for instance, on the merits of oregano, cinnamon, and chilis for chicken growth and health, or this study, which found that oregano oil cut poultry deaths from avian coccidiosis (a disease caused by a protozoan parasite) by 59 percent. And along with studies on animals will come studies on humans.

Parrish and Riedel recently published a review on how essential oils could combat superbug infections in people. The oils, they say, could be combined with existing antibiotics or be administered separately, but there’s still a long way to go on this front. The scientists must first figure out which of the 1,000 components within each of the oils they study—including oregano, thyme, lavender, and cinnamon—are key.

Imagine looking at a bowl of cake mix, says Parrish. Even though you know there are eggs, milk, salt, baking powder, and sugar in there, you don’t see them as separate and distinct. “That’s basically what an essential oil is,” she says, “a mix of hundreds and hundreds of things.”

And not all those ingredients may be essential. Discovering what is, and then determining how it works, will be the next steps.

And that’s what Hofacre continues to chip away at in Georgia. He recently got a shipment of thyme oil. I wonder if his office smells like roasted potatoes nowadays.


onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.

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