Gardening

From the scientists: How to use catnip as a mosquito repellent

From the scientists: How to use catnip as a mosquito repellent thumbnail
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We talked to the scientists whose research showed catnip to be as effective as DEET in deterring mosquitoes to find out how to use catnip as a mosquito repellent. Find out what they had to say AND how you can grow and use catnip to fend off mosquitoes! 


Mom’s ‘Meowie Wowie’ catnip

I grew up with cats and an avid gardener for a mom. Thus, mom always had a patch of catnip (Nepeta cataria) growing in our yard, and our family delighted in occasionally offering fresh cuttings to our cats so as to watch them get high on “nip.” 

Years back when The Tyrant and I were living in an apartment, mom gave us some of her fresh catnip to offer to our cat, Charlie. It just so happened that Susan had food poisoning at the time, and I’d gotten her Easter lilies as a get-well-soon sympathy gift. We didn’t know it, but Easter lilies are highly poisonous to cats…       

When I came home that evening, The Tyrant woke up and we both discovered Charlie the cat laying on the floor completely immobilized in a small puddle of drool. I tried to get her to stand, but she flopped back down in a heap. 

After a quick google search, we learned about Easter lily toxicity to cats and began to panic. “Charlie must have eaten some of the lilies!” we thought. 

It was a Friday night, so we couldn’t bring her to the vet. In a panic, we called animal poison control, which is not free, for the record. Over the duration of the 45 minute phone call with the poison specialist, Charlie the cat slowly regained motor function and was eventually able to sit up.

It turned out, she hadn’t eaten Easter lilies; mom’s catnip was just far more potent than the crummy nip she’d been getting from the pet store. No, we weren’t thrilled to have to pay a significant sum of money only to find out our cat was just really, really high. 

We saved seeds from mom’s “Meowee Wowie” catnip (as we started calling it) and have been growing it in our own garden for the past 10+ years. During that time, we’ve been thrilled to know that catnip has other benefits: namely, it’s a potent mosquito and insect repellent. 

 

 
 
 
 
 
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New research: catnip better than DEET at repelling mosquitoes   

I try my best to monitor the latest plant and agriculture-related research. In early March, a headline caught my eye: “Could catnip become the new insect repellent?

The article detailed new collaborative research from Northwestern University and Lund University that proved catnip to be at least as effective as DEET in repelling mosquitoes. (Prior research showed catnip to be 10x more effective than DEET.) The big question this new research was finally able to shed light on: how and why catnip is such an effective mosquito repellent.  

Catnip starting to grow back in early March. Catnip is a perennial plant that dies back to the ground in winter.

Catnip starting to grow back in early March. Catnip is a perennial plant that dies back to the ground in winter.

The answer: certain compounds in catnip (primarily nepetalactones) trigger mosquitoes TRPA1 pain/itch receptors. Think of it like this: you wouldn’t willingly go into a restaurant to have dinner if someone had just sprayed pepper spray inside, would you? Catnip has a similar effect on mosquitoes that pepper spray has on humans.   

Humans and other species also have TRPA1 receptors, however we don’t have the same sensitivities to these botanical compounds. This discrepancy potentially points to why catnip is adapted to have this feature in the first place: to repel certain insects that might otherwise eat it. 

This nature-based chemical warfare system can be used to your advantage: you can grow and use catnip to repel mosquitoes! In our own garden, we vigorously rub leaves of mom’s Meowie Wowie catnip between our hands, then rub it on our exposed skin. In the summer, this buys us about 30 minutes of mosquito-free time, presumably until the botanicals volatilize to a certain threshold where they’re no longer an insect deterrent. 

It doesn't take much catnip to repel mosquitoes! This sprig of catnip is all that's needed to provide about 30 minutes of mosquito protection. Rub vigorously between your hands to release the botanical compounds, then rub it on your exposed body parts.

It doesn’t take much catnip to repel mosquitoes! This sprig of catnip is all that’s needed to provide about 30 minutes of mosquito protection. Rub vigorously between your hands to release the botanical compounds, then rub it on your exposed body parts.

Questions for the catnip-mosquito scientists… 

After looking through the new catnip research, I still had some lingering questions. Thus, I reached out to the study’s authors for answers, starting with Dr. Marco Gallio at Northwestern University. Dr. Gallio then linked in:

  • Marcus Stensmyr, the namesake of the Stensmyr lab at Lund University; and
  • Dr. Nadia Melo, the first author of the paper and — as Dr. Gallio described her — “the person who did all the cool mosquito experiments in the Stensmyr lab at Lund. Among other experiments, she put her own hand in a cage full of hungry mosquitoes to test the efficacy of catnip oil.” 

Dr. Melo was gracious enough to answer my questions despite being on maternity leave! Below are excerpts from our exchange:  

Question 1:

Are (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone the sole compounds responsible for the mosquito-repellent properties of catnip or are there other compounds working synergistically to produce the repellent effects? For instance, Birkett et al. 2011 found:    

“… these data suggest that although the nepetalactone isomers have the potential to be used in human and livestock protection against major pathogen vectors, intact, i.e. unfractionated, Nepeta spp. oils offer potentially greater protection, due to the presence of both nepetalactone isomers and other components such as (E)-(1R,9S)-caryophyllene.” 

Dr. Melo:

The nepetalactones are the main compounds responsible for the repellent effect. However, other compounds such as the one mentioned in Birkett et al.2011 (caryophellene) also have a repellent effect on a diverse range of insects.<

Question 2: 

What would be the most effective way for a home gardener (without access to a chemistry lab!) to utilize catnip as a mosquito repellent? a) rub fresh plant on skin, b) chop and cook in olive oil at 200°F, then use infused oil as a topical application, c) another method?

Dr. Melo:  

I believe that both methods that you suggested work, however, when I tested the two different variants in the lab I found that catnip [essential] oil is more effective and the effect lasts longer. I also found that the oil provided a better spatial repellence. So in short, if possible I would recommend the oil.

Question 3:

Related to #2, would a person be better off buying and using catnip essential oil or can they achieve comparable results with fresh catnip?   

Dr. Melo: 

In addition to my previous answer, fresh catnip provided protection but the essential oil provided a longer lasting effect.

Question 4:

I’m trying to figure out how to use catnip essential oil for my family (including our toddler) AND how to advise other people to use it. For instance, would it make sense to buy an unscented skin lotion and mix in catnip essential oil to make a DIY mosquito repellent at a certain concentration? Or is there a better way to do it?

Our toddler and our cat enjoying playing in one of our catnip patches.

Our toddler and our cat enjoying playing in one of our catnip patches.

Dr. Melo: 

Unfortunately my expertise does not lie in product production and since we did not test this outside the laboratory it is difficult for me to say how you could DIY a repellent based on catnip oil. It’s always tricky when it comes to application on the skin. I used the essential oil directly on my hand, however the amount was very small. I don’t want to recommend any particular dosage since we haven’t done further testing for market use but I believe that incorporating catnip essential oil into lotion could work.

In general, I would say that 1: catnip oil could be used together with aroma sticks that way you don’t need to apply it to your skin; 2: you can plant catnip around the house; 3: rub catnip like you usually do [referenced above] but as you mentioned protection doesn’t last very long.

Question 5:

Birkett (referenced above) also found that catnip was an effective repellent against Ixodidae ticks, which are becoming a huge problem here in the US with the increasing prevalence of Lyme disease. Do you think the data show this to be the case, e.g. can gardeners also use their catnip to help protect themselves against ticks?

Dr. Melo: 

Studies have shown that catnip has a repellent effect on ticks as well (we include a few references in the table found in Figure 1). I did some preliminary studies against ticks using Nepetalactone and did not find significant results, however, the case may very well be that when used at the right concentration etc it provides protection against ticks. Ticks are a bit more sturdy than mosquitoes. 

3 key takeaways for repelling mosquitoes with catnip:

Here are our key takeaways for home gardeners and outdoor enthusiasts interested in using catnip to repel mosquitoes:

  1. Compounds in catnip are at least as effective as DEET (and potentially up to 10x more effective) at repelling mosquitoes.
  2. Fresh, home-grown catnip can be vigorously rubbed between your hands then applied to your skin to provide ~30 minutes of mosquito-free time. Re-apply fresh catnip as-needed while you’re in your garden for longer durations. 
  3. For longer-lasting effects or to have a ready-made mosquito repellent available during hikes, foraging adventures, etc, apply a small amount of catnip essential oil to your skin or mix catnip essential oil into an unscented skin lotion to make your own mosquito lotion.  

Other uses of catnip

Even if you don’t have cats or want to use catnip as a mosquito repellent, catnip has other benefits:

1. Catnip tea 

Catnip is in the mint family and tastes the part. Thus, it makes a delightful, minty-flavored tea.

2. Stress relief

Catnip has a long history of use as an herbal medicine, primarily for relaxation and stress relief. However, pregnant women should avoid consuming catnip since it can trigger uterine contractions.   

3. Pollinator plant

In the summer, our catnip plants send up 2-3′ tall stalks covered with small white flowers. Native bees, honeybees, and other pollinators absolute love foraging its flowers. (No, not all insects are repelled by catnip!) 

One of our ducks providing size perspective for a flowering catnip plant in July. (The white flowers are catnip.)

One of our ducks providing size perspective for a flowering catnip plant in July. (The white flowers are catnip.)

Invasive catnip plant warning:  

If you grow catnip, be warned: it can be invasive like other plants in the mint/Lamiaceae family.

Many mint species spread via underground runners. However, catnip spreads via seed, NOT underground runners. 

This distinction means that growing catnip in pots will not contain its spread. Instead, you’ll want to cut off the flower stalks after they’ve bloomed (so your pollinators get food) but ideally before the seeds have matured. If in doubt, simply remove the finished flower stalks and dispose of them in the trash rather than composting them (so you don’t end up with compost full of catnip seeds). 

Where to buy catnip: 

  • Catnip is very easy to grow from seed. You can buy catnip seeds here. Simply follow the growing instructions on the package. 
  • Local plant nurseries often sell catnip starts in the herb section, so call around and check. 
  • Or you can skip the growing part and simply buy catnip essential oil.  

We hope you and your family benefit from using catnip to repel mosquitoes! If you have cats, just be careful to introduce a small amount of ‘nip until they develop a tolerance. Otherwise, you could end up like us: on the phone with animal poison control because your cat overdoses. 

Special thanks to Drs. Gallio, Stensmyr, and Melo for their work in proving the efficacy of catnip as an insect repellent and answering the important question of why catnip works! 

KIGI,

Tyrantfarms
 

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2 Comments

  • Reply
    Jennie Broadhurst
    July 16, 2021 at 9:19 am

    Did you have any idea for a kid safe amount of catnip essential oil for a repellant?

    • Reply
      Aaron von Frank
      July 16, 2021 at 1:33 pm

      Hi Jennie! I can’t say for certain and the scientists I spoke with weren’t comfortable making those sorts of claims either. They were just doing tests/research to determine whether — and to what degree — catnip essential oil repels mosquitoes. Since people (including children) can be allergic or sensitive to various essential oils, it might be best to try a small amount first to test for any reaction, then use as-needed to repel mosquitoes once you know your child isn’t going to have any problems with catnip essential oil. Wish I could give you more specific information and direction, but that wouldn’t be responsible. Another option: You could always try to find a commercial mosquito repellent that contains catnip essential oil since they’ve hopefully tested and figured out ideal ratios when doing their product’s research and development.

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