Natural vs. Synthetic Repellents — What Does the Research Say?
By Paul Johnson ([email protected])
It is the time of year when young ticks — the tiny nymphs — begin to roam and people become more aware of the need to repel them. Actually, ticks can be active just about year-round in many climates, so we should never let our guard down when it comes to keeping them away. As soon as the ground thaws, the ticks that we are most concerned about — the deer tick or blacklegged tick — emerge and begin looking for hosts.
Because we humans are one of the main hosts for ticks, we need to take measures to keep them away. Tick repellents should be something that anyone living in a tick-heavy area uses often. But which repellents are best? And are the natural repellents as good as the synthetic types?
It has been a topic of debate for years, and testing has been hard to come by on many of the alternative repellent ideas.
We want to follow the science, so here is the run-down on the most common repellents on the market today and what research says about them.
Man-made tick repellents are our go-to, and have been for a long time. As much as we would love the idea of rubbing a little peppermint oil on our skin to repel ticks, we like the synthetics because they are proven; they work. Some of our most common questions at the Tick and Mosquito Project are on if these repellents are safe. We aren’t chemists, but rather rely on organizations like the EPA and the CDC who believe that when used as directed, they are safe.
It should be noted that some of the experiments do not delineate between the blacklegged tick — the one we are very focused on here — and other ticks like the dog tick or lone star tick.
Perhaps the most common repellent for ticks as well as insects and other disease vectors is DEET. DEET has been around since the 1940s and used pretty widely for the past 60 years, and the EPA, in multiple studies, has deemed it safe for adults and children. Most recently, an NIH study confirmed that DEET does not pose health risks when used as directed, including in pregnant women.
The nice thing about DEET is that it can be used directly on the skin. Studies have shown that using DEET significantly reduces the number of ticks that attach on the skin, with some research suggesting that DEET repels about 3 of every 4 ticks. There is some evidence that the best concentration of DEET against ticks (you can find many concentrations even from the same manufacturer) is one of at least 25% DEET.
Note that DEET is not tested on people less than 6 months of age. The recommendation is to not use it on newborns and young babies…. Not because of known issues, only because it has not been tested.
Like DEET, picaridin is a chemical used on mosquitoes, but one that also shows some effectiveness on ticks. Most studies suggest it is not as effective as DEET on ticks, but still much better than using nothing. It is commonly found in repellents on the shelf next to DEET-based repellents, and it can be used directly on the skin.
If you think of DEET as the right repellent for skin, then think of permethrin as the repellent for clothing and footwear. Permethrin as actually a chemical that is inspired by naturally-found pyrethrins, but it is man-made for maximum effectiveness. Like DEET, it is also used on mosquitoes, but unlike DEET, it is particularly effective on clothing and boots.
An NIH study of the effectiveness of permethrin on boots and socks found that subjects using permethrin-treated footwear were a whopping 73 times less likely to have an attached tick bite. It is also deemed safe to use on clothing, as long as it is used per instructions.
Perhaps the best combination, for those willing to use synthetic chemicals, is one of permethrin on the clothing and footwear, and DEET on exposed skin.
Natural repellents are a favorite of many, because of the desire to eliminate insecticides and synthetic chemicals from our space and personal environment. While we commend people for wanting to make their living area toxin-free, we also know that you want to be sure the effectiveness of any natural solution is high enough to be able to trust it. While the amount of research does not compare to that of DEET or Permethrin, there are some repellents that are showing some promising signs.
Oil of Lemon Eucalyptus
Good oil OLE, it has proven pretty effective against mosquitoes and shows some promising signs against ticks as well. Of the natural repellents, OLE (due to its primary oil, PMD) appears to be the most effective against ticks. The National Institute of Health suggests that after DEET as the top choice and picaridin as the second, a repellent containing PMD is perhaps the next most effective.
Garlic has been gaining a grassroots following as a potential tick repellent. It has shown some promise as a repellent when applied to an area outdoors, but we can’t find any proof that it is an effective on-skin repellent. While it might be better than nothing, the research we are following also suggests that ingesting garlic has no effect on repelling mosquitoes or ticks.
Essential Oil of Catmint
Catmint is a perennial that you have probably seen. It grows just about anywhere, and its lavender / purple flowers stand out when they are in bloom. Catmint contains a chemical that, when concentrated, has shown some repelling ability against ticks.
While the most concentrated form of catmint oil has shown effectiveness against ticks, the essential oil that you might buy online has probably not been tested. It might be better to use than nothing at all, but we suggest waiting to see what further testing shows.
The important thing when it comes to using a tick repellent is if it is effective. We are holding out hope that some natural tick repellents emerge with a high degree of effectiveness, but until then, the recommendation has to be to stick with the tried and true. DEET (or to a lesser degree, picaridin) for the skin, and permethrin for footwear and clothing. Lyme disease is too serious to play around with repellents that may or may not work.