health: 4 ways to make a natural and nontoxic mosquito repellent
Catnip (Nepeta spp) is attractive to most cats, but also acts as a natural repellent to mosquitoes. We’ve known for many years that oil made from catnip, called nepetalactone, in well-known research conducted about 10 years ago by Iowa State University, is more effective than DEET for short term exposure.
In a New England Journal of Medicine study from around the same time, catnip was not included as one of the natural botanical choices studied. But the study's observation of the limits of natural repellents agrees with my experience. Products containing DEET last far longer, while natural remedies need to be reapplied as often as every 20 to 30 minutes to remain effective.
I’ve been making, using and sharing catnip-based repellents for about 30 years, and appreciate that I can make it myself rather easily and very cheaply. It's also safer and nontoxic (I use the oil on my dog).
Reports from friends who have traveled to heavily mosquito-infested areas are very positive. It works, but has to be reapplied frequently. I used to include citronella and eucalyptus in my sprays, but now use catnip and yarrow flowers (see the end of the article) exclusively.
Here's how you can make your own natural mosquito repellent.
In a pinch, you can take sprig of catnip and crush them in your hands, releasing the oils and a strong scent. Tuck the plant into a hat, around the neckline of your clothes, and other places that are exposed. You can also rub the plant directly onto your skin, but that loses effectiveness rather quickly and leaves green stains.
Still quick, and a bit more effective, would be to make an oil-based infusion of the plant. The fastest way to do this is using your oven.
Gather the catnip leaves and stems and chop them finely to expose more surface area of the plant. Cover the bottom of a casserole dish with the plant. Cover the greens with oil. I use olive oil for its stability, though soy oil may also be a good choice as it may have some mild repellent ability on its own. I have not verified this claim.
Heat in a very slow oven (about 200 degrees) for 2 to 3 hours. I usually make this in the evening, and just turn off the oven for the night and let the mixture sit overnight in the oven.
When it is cool, strain out the leaves, and refrigerate the oil until you use it. The down side to this method is a house that smells strongly of catnip. It can be a bit much for people sensitive to smells. I wouldn’t recommend it if you have cats.
Linda Diane Feldt | Contributor
The longer method of making an oil is to fill a very clean jar with the chopped greens that have been only slightly compacted. Fill the jar with olive oil and cap with a lid. Shake to bring air bubbles to the top, and fill completely with the oil. Let that sit for two to six weeks. If you shake the jar every day, it will be ready in a shorter time. If you just let it sit in a cool dark place, give it six weeks to infuse.
I don’t care much for applying oil on a hot summer day, so an alcohol-based infusion is my preferred medium. The recipe is similar to the oil: Gather the leaves and stems of the plant, chop and fill a jar with the greens. Use 100-proof vodka to fill the jar. Screw a lid on tightly and set aside for two to six weeks. Like the oil, if you shake the jar every day it will infuse more quickly; otherwise wait six weeks.
After straining the alcohol from the plant, I fill a small spritzer bottle just halfway with the liquid, which is now called a tincture. I use water for the other half. This diluted liquid has a cooling effect when sprayed.
You will need to reapply the catnip repellent, whichever form you choose, about every 30 minutes to maintain optimal effectiveness.
The science behind using catnip remains a bit sketchy. Since catnip is an easy to grow weed (I’ve been removing it form my garden for over 25 years and still have more than I could ever use), there is no clear profit in the research.
In the journal article, the researchers endorse DEET products primarily because of their longer effectiveness. (See: Vol. 347, No. 1, July 4, 2002: "Comparative Efficacy of Insect Repellents Against Mosquito Bites.") That agrees with my observations, but I’d rather reapply frequently rather than use DEET.
With such a wet spring, it promises to be a summer with plenty of mosquitoes. If you’d like a cheap, effective and safer method of keeping them at bay, you might want to give catnip a try.
In a few weeks, yarrow (Achillea millefolium) flowers will also be available. Yarrow seems to work almost as well as catnip, and can be prepared in the same four ways outlined above. The wild white flowered yarrow is considered to be the most potent.