One morning in my university dorm I woke up to the faint smell of pizza wafting from the kitchen, only to come out of my room and find my roommate downing a shot of oil of oregano with her breakfast. She swore the bitter herb would fend off the illness she felt she was coming down with. According to her, pizza-flavoured breath was just an added bonus.

Curious, I began my own oil of oregano ritual. When I felt a tickle in my throat or woke up the slightest bit congested, I’d swig a little of that “magic” (but disgusting tasting) oil, drink a glass of water, and get on with my day. I never put much thought into the efficacy of the ancient remedy, and I never noticed whether the oil I had supplemented into my life was actually warding off illness. However, this blog has piqued my skepticism of any natural remedy, so I figured it was time to dive into the science behind the healing properties of oil of oregano.

To my pleasant surprise, there has been a hefty amount of scientific research done on the effects of oil of oregano! Here’s the download, in the form of an FAQ, from my research:

Is there evidence that oil of oregano has any bioactive properties (aka does the oil actually do anything to living cells)?

There are two main molecules in oil of oregano: carvacrol and thymol. These two molecules can’t harm human cells, but they can actually kill fungal and bacterial, or microbial, cells. Carvacrol and thymol are relatively small molecules that can slip inside the cracks of the bacterial walls and cause disruption of the cell membrane. I’m no carpenter, but I imagine if you wanted to destroy an enemy’s house, you could secretly cut the supporting beams holding up the structure until the whole thing collapsed in on itself. That’s what these molecules in oil of oregano do to bacteria. They sneak inside and cause irreparable damage until the single-celled organisms just fall apart.

So yes, oil of oregano definitely affects living cells! It kills pathogenic (“bad”) microbes, but it might also harm some of the good bugs we have too…

So, is oil of oregano can kill bacteria and fungi that cause infections in humans?

Yes! Not only is oil of oregano strong enough to kill bacteria and fungi, but it effectively kills bacteria and fungi that commonly infect humans—like candida, steppococci, and E. coli . In fact, in 2018 a group of researchers out of Massachusetts General Hospital smothered a whack of different human-infecting bacteria and found that oil of oregano was good at killing them. The oil of oregano even destroyed some antibiotic-resistant bacteria and worked even when the bacteria made a protective collective barrier called a biofilm.

Does that mean that ingesting a teaspoon of oil of oregano will help fend off a cold or flu?

Probably not.

The common cold and the flu are viruses. Viruses are little half-organisms filled with DNA instructions that can hijack your cells and make you sick, but they ARE NOT microbes! Thus, something antimicrobial won’t kill off a virus. Since there is pretty much no evidence that says that oil of oregano is antiviral, it probably doesn’t do a great job of fending off a cold or flu. Just like prescription antibiotics can’t cure a cold or a flu, neither will a dose or two of oil of oregano.

However, when your body is fighting an infection, your immune system is often overrun and has trouble in its normal housekeeping duties. This can cause you to come down with a secondary infection, usually fungal or bacterial. For example, oftentimes when I have a cold (which is a viral infection), I also end up with a sinus infection or conjunctivitis—both of which can be bacterial infections!

Since oil of oregano is antimicrobial, it may play a role in fending off these secondary bacterial and fungal infections, but I haven’t read any studies that have tried to prove this. However, researchers at Massachusetts General Hospital were able to demonstrate that applying oil of oregano to an open-flesh burn wound killed off bad bacteria and prevented infection.

If oil of oregano is similar to an antibiotic, will overuse lead to the same adverse consequences as overuse of antibiotics?

We know that frequent antibiotic use can lead to some unintended harmful results. It can increase the possibility of antibiotic-resistant bacteria, and mess with the healthy bacteria in your gut. If oil of oregano kills bacteria, wouldn’t it have the potential to produce those same negative consequences?

Sorry to be wishy washy, but based on my research, I’m not sure.

Anything that can kill of bacteria runs the risk of the bacteria mutating in a way that makes them resistant to the enemy. However, it seems that bacteria have a tough time finding ways to resist the lethal properties of oil of oregano. A group of Brazilian researchers found that bacteria have a slow rate of resistance to oil of oregano. However, these researchers caution that we should be careful how we use natural antimicrobials because we still don’t know the extent of the possible harmful ramifications, including the possibility of leading to bacterial resistance.

As for how oil of oregano affects our microbiome, there isn’t any strong research to enlighten us on the effects of ingesting oil of oregano and our microbiome. The jury is out on this one, for the time being at least.

So, I should stop using antibiotics and just use oil of oregano?

The scientific evidence suggests that taking oil of oregano could have positive effects as a preventative measure against infection. However, if you suspect you already have an infection, you should seek guidance from a healthcare professional.

While I agree that antibiotics are often overused or misused, they are still an incredible and important tool to be used in an appropriate setting.

Are there any other uses for oil of oregano?

Yes! The most common use of oil of oregano right now is in the food industry. It is used as a food preservative and a growth promoter in livestock feed. In fact, since supplementing antibiotics in livestock feed was banned in the United States in 2017, many farmers have instead begun to feed their livestock oil of oregano.

The Verdict?

Oil of oregano isn’t going to cure your cold, but it might give your immune system a little break by helping fight off other infections when you are a bit run down. The addition of pizza breath? Well, your friends, family and roommates can weigh in on whether that goes on the pro or the con list…