A Secondary Benefit of Catnip That Few People Know About

Analysis by Dr. Karen Shaw Becker

catnip repel pests

Story at-a-glance

  • While most people are aware of the euphoric effects of catnip and silver vine on feline family members, a less well-known effect of these plants is their ability to repel pests
  • A recent Japanese study shows that a special cocktail of chemicals is produced when cats chew on the leaves of these plants, especially silver vine
  • The chemical mixture emitted by damaged silver vine leaves is both more attractive to cats, and repellent to mosquitoes, than the chemicals produced by damaged catnip leaves
  • Catnip and silver vine-based mosquito repellents may hold great promise for human populations in developing countries with widespread mosquito-borne disease
  • Catnip oil is also an effective pest deterrent for dogs and cats

Catnip is best known for its euphoric effect on cats, and another herb that’s a hit with domestic felines is silver vine. In fact, according to a 2017 study, a greater percentage of cats react to silver vine than to catnip.1

Research suggests it’s the nepetalactone molecule in both plants that stimulates opioid receptors in the brain in the same way morphine does. When a susceptible kitty gets hold of catnip or silver vine and absorbs the nepetalactone, her pleasure centers (opioid receptors) in the brain are activated and the next thing you know, she's rolling around in a state of goofy bliss.

What many people don’t know is that these plants are also known for their powerful repellent action on insects, especially mosquitoes. In fact, recent research shows catnip compounds to be at least as effective as synthetic insect repellents (e.g., DEET).

Researchers at Northwestern University and Lund University in Sweden discovered the mechanism within catnip that causes insects to avoid it. Their study results were published last year in Current Biology.2

"Catnip and its active ingredient, Nepetalactone, have been used for millennia to ward off insect pests, at least since the time of Pliny the Elder," study co-author Marcus C. Stensmyr, associate professor at Lund University said in a news release. "But why Catnip is so potent on such a broad range of insect species has remained unknown."3

Study Reveals Why Cats Chew on Silver Vine Leaves

Now, a just-published study by researchers at the University of Iwate in Japan shows that when cats roll around in, chew on, and otherwise damage either catnip or silver vine, the leaves of the plants emit even higher levels of chemical compounds that repel mosquitoes.4 It seems that when cats chew up the leaves of the plants, their natural bug spray properties grow more potent.

According to study co-author Masao Miyazaki, an animal behaviorist at the university, cats interact in four main ways with catnip or silver vine — licking, chewing, rubbing, and rolling.5 An earlier study found that rubbing and rolling around on the plants transfers iridoids to the cats’ fur, triggering an endorphin rush while simultaneously applying natural mosquito repellent. However, this doesn’t explain why cats also lick and chew the leaves, other than to “get high.”

The researchers set out to determine what happens, chemically speaking, when silver vine leaves get damaged. Toward that end, they collected and analyzed intact leaves, leaves chewed on by cats, and leaves they crumpled by hand.

Their investigation revealed that the damage caused by both the cats and the humans resulted in increased release of a variety of iridoids. This cocktail of several iridoids had a relatively even balance of five different chemicals rather than a single chemical, and the cats preferred it, even when the levels of nepetalactol were the same under both conditions.

Scientists have assumed that it’s the nepetalactol that is attractive to cats, but surprisingly, this new finding suggests it’s actually the mixture of chemicals that’s most enticing. 

Complex Chemical Mixtures Are More Effective

Interestingly, the complex chemical cocktail from the silver vine leaves that was most attractive to cats proved to be the best mosquito repellent as well. The researchers learned this through an experiment in which they filled a clear box with mosquitoes and placed a shallow dish inside. When they added the complex cocktail to the dish, the mosquitoes fled more quickly than when the simpler mixture was added.

Next, the researchers repeated all their silver vine tests with catnip and found very different results. Unlike silver vine, catnip leaves didn’t produce a diversified chemical cocktail in response to cat-inflicted damage. The main iridoid in catnip is nepetalactone, not nepetalactol, and leaf damage has no effect on this. When cats chew on catnip, the leaves significantly increase their emissions of nepetalactone alone.

Damage to catnip leaves did make them more attractive to cats and more repellent to mosquitoes, but when compared to silver vine, a large dose of the catnip chemical cocktail was needed to elicit the same response from cats and mosquitoes as a very small dose of the silver vine cocktail.

To date, science hasn’t answered the question of why even small amounts of complex mixtures of chemicals are so effective at eliciting responses.

Another puzzle yet to be solved is at what point feline behavior regarding plants like catnip and silver vine first evolved. In an earlier study, the same researchers discovered that leopards and jaguars rub their heads on nepetalactol-soaked paper just like domestic cats do.

Since most big cats don’t “get high” when interacting with the plants, this finding suggests that it’s the insect-repellent properties of certain plants that initially prompted the behavior in a distant feline ancestor.

Another mystery is why cats — but not other mammals that acquire diseases from insects (including dogs) — developed this innate defensive behavior against pests.

Catnip and silver vine might be useful for protecting humans from insects as well. The chemicals they produce could potentially be used to develop safer and more effective insect repellents intended for humans. Plant-based repellents are often easier to obtain and less expensive than chemical compounds, which means the accessibility of catnip could be hugely beneficial in developing countries where mosquito-borne diseases are widespread.

Natural Pest Deterrents for Pets

If you’re a regular visitor here, you know that I routinely recommend catnip oil as a natural, nontoxic pest deterrent for dogs and cats. Here are a few others:

All-natural pest deterrents dogs — You can make an all-natural pest deterrent for your dog very easily at home. It will help him avoid a good percentage of the pests he encounters, though not all of them. The recipe: mix 8 ounces of pure water with 4 ounces of organic, unfiltered apple cider vinegar and 20 drops of neem oil.

Neem oil is not a true essential oil. It’s an expelled or pressed oil, and it’s safe for cats (I have a pest deterrent recipe for kitties I’ll give you in a second). Neem oil is effective because fleas and ticks hate it. It’s also great for animals who are very sensitive to smells.

If you want to add some extra punch to your dog’s pest recipe, go with an extra five drops of catnip oil, lemon, lemongrass, eucalyptus, or geranium essential oil from a high-quality essential oil brand you trust. I use geranium oil quite a bit because I find it very effective.

In fact, I use it in my Dr. Mercola natural flea and tick products. If you have a dog who’s exposed to ticks, adding the extra punch of one of these essential oils can be very beneficial. If you’re most concerned about mosquitoes, adding in 10 drops of catnip oil can be an excellent deterrent.

You can store your homemade pest spray in the fridge, which is what I do. Before my dogs head out in the morning, I shake the mixture well and mist them with it, being careful to avoid their eyes.

The oils in the recipe dissipate in about four hours, so you may need to reapply it several times throughout the day if your dogs spend a lot of time outside. This recipe can also be used in conjunction with other pest protocols to help make your dogs generally more unsavory for a variety of annoying summertime parasites.

For cats — My recipe for cats is very similar to the one for dogs. Mix 8 ounces of pure water with 4 ounces of organic, unfiltered apple cider vinegar, plus 10 drops of neem oil and 10 drops of catnip oil. Mixing cats and essential oils can be tricky, so we want to leave the true essential oils out of the kitty recipe. Neither neem nor catnip oil are truly essential oils (they’re distillates), so we’re safe using those.

These are two easy, all-natural recipes you can use to deter pests and as a bonus, they also make your pet smell wonderful! You can use them during flea season, tick season, and all summer long.

If you live in areas where pests are such a problem you have to use chemicals, consider starting with the Spinosad class of chemicals, which are derived from soil bacteria, and whenever you use chemicals, make sure to detox your pet simultaneously.

 

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