Best Indoor Repellent
How to Choose Best Mosquito Repellent Spray
Mosquitoes can carry some of the most deadly diseases in the world. While you have likely become used to the local mosquitos in your area, traveling will expose you to new types of mosquitoes and all the different illnesses they can potentially carry.
Imagine you visit an area where there are hundreds of mosquitos buzzing around — and none of them bite you.
Diseases Transmitted by Mosquitoes
Insect repellents do more than just keep you free from mosquito bites and irritation. They are an incredibly potent way to avoid mosquito-borne diseases, which exist almost everywhere in the world where mosquitoes live. In particular, powerful mosquito repellents can be used to keep away the flying critters that harbor Zika, Dengue Fever, West Nile, Malaria, or many other potentially deadly illnesses.
The World Health Organization declared in 2016 that the Zika virus is rapidly spreading within the Americas, particularly within Latin America, the Caribbean, Puerto Rico, and the southern states within the United States. The disease itself has been linked to serious birth defects and is transmitted primarily through mosquitoes. It is a large public health threat for American citizens, especially for those who are looking to have children. Proper mosquito repellent use can reduce the risk of receiving the virus significantly by preventing the vast majority of mosquitoes from biting a person. The same species of mosquito that carry Zika can also potentially transmit Dengue fever. Some strains of dengue fever can have a mortality rate as high as 50% if left untreated.
Malaria is perhaps one of the most infamous mosquito-borne illnesses. In a study done by the World Health Organization in 2016, nearly half of the world’s population is at risk of malaria. For areas that are affected by malaria, the disease is a large cause of illness and death in the region. While considerable success has been achieved in pushing malaria back, actual elimination of the disease will only happen in the far future. Sub-Saharan Africa, in particular, carries a huge risk of malaria risk — nearly 90% of the world’s malaria cases occur there. In order to keep yourself safe in endemic regions, it’s essential to take as many safety precautions as possible, which includes investing in a proven insect repellent as one of the steps.
West Nile is the leading mosquito-borne disease in the United States that has spread throughout almost all of the U.S. over the past two decades. There are no vaccines to prevent or treat people who have been infected. About 1 in 5 people who are infected by the disease develop a fever and other symptoms, with 1 out of 150 infected developing a serious, potentially fatal illness. Once infected, the symptoms could range anywhere from a few days of discomfort to several weeks of illness in severe instances.
The key part of avoiding mosquito-borne illnesses is staying away from mosquito-infested areas and minimizing any potential exposure to the biting insects. Mosquito repellents are just one part of a multi-layered strategy to fend off biting insects. It’s important to also wear long-sleeved pants and shirts when outdoors, to minimize open skin that mosquitoes can land and bite on. Many mosquito repellents can also be applied onto clothing, as an extra barrier of protection. Most mosquitoes are also only active during certain parts of the day, particularly dusk, so avoiding the outdoors during that time can prevent unnecessary exposure as well.
The Active Ingredients
There are hundreds of mosquito repellents available in the market today, many of them using all sorts of ingredients and combinations to try and keep insects away. Fortunately, there are two agencies based in the United States that evaluate how safe and effective bug sprays are, which is where we start our search.
The CDC and Environmental Protection Agency (EPA) recommend the four following ingredients: DEET, Picaridin, Oil of Lemon Eucalyptus, and IR3535.
This means that strong perfumes and aromatics won’t be enough to deter the most stubborn of mosquitos, which is why our guide is going to focus primarily on just mosquito sprays with these active ingredients.
DEET
DEET is known chemically as N,N-Diethyl-meta-toluamide, and is a yellowish liquid that repels all sorts of biting insects when applied to skin or clothing. It was a chemical first created in the 1940s for the U.S. military, and has become available commercially since 1957.
When evaluating active ingredients, DEET is a repellent in every sense of the word. It does not kill insects on contact, but rather prevents them from landing on people. While there is still a bit of confusion on how exactly DEET works, it is hypothesized to confuse insects when they are close to the chemical, which makes it hard to land onto the person. Another theory is that DEET just simply smells awful to most bugs, so that they stay away.
Regardless of how DEET works, it is one of the most widely used active ingredients in insect repellents in the U.S. This is because DEET is so effective — many scientists believe that DEET can be used as the gold standard to measure repellents against. Testing has shown that DEET-based repellents have consistently ranked among the top performing insect-repellent products available in the market.
DEET is not perfect, however. There have also been reservations about the overall safety of DEET. While the chemical has been deemed safe in testing when used as directed, there have been people who remark that DEET causes irritation and itchiness. When too much DEET is used, it can cause something called “DEET poisoning,” which can potentially cause seizures and death.
In general, DEET has caused some of the following limitations and drawbacks:
- DEET can cause minor skin irritations and rashes. Absolutely do not use DEET on broken skin or eyes. It can be toxic if swallowed.
- Sprays with over 10% DEET should not be used on children
DEET can melt some synthetics, which can ruin plastic or vinyl products.
Fortunately, the sheer amount of DEET that needs to be used to experience serious DEET poisoning is massive. Most cases of DEET toxicity occured when consumers failed to follow instructions (such as consuming it). The reality is that the vast majority of people getting DEET poisoning is very mild, which can be treated at home with just some rest. In the end, the only way to get DEET poisoning is to outright ignore the instructions clearly labeled on the container.
Picaridin
Picaridin is a synthetic compound that was first discovered in the 1980s. It was created to closely resemble a naturally occurring compound called piperine, which are produced by the same group of plants that produce black pepper. Ever since its discovery, Picaridin has been widely used in Europe and Australia but was only made available commercially in the United States in 2005.
Much like DEET, Picaridin repels insects without killing them. Unlike DEET, Picaridin seems to prevent mosquitoes from sensing people at all. Picaridin-based sprays are typically applied on either skin or clothing, which will form a vapor barrier that prevents mosquitoes from landing on the surface applied.
Picaridin is completely safe when used in instructed quantities. It is highly recommended to your hands if you apply a picaridin-based spray on them, but ingesting a small quantity is harmless to people.
Much like DEET, overusing or improper use of Picaridin-based sprays can cause skin irritation. Studies have shown that proper usage of Picaridin will not cause an increased chance of cancer.
Picaridin has some of the following limitations and drawbacks:
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- Skin and eye irritation
- Vomiting, in rare cases
Oil of Lemon Eucalyptus
Unlike both DEET and Picaridin, oil of lemon eucalyptus is a natural method to protect against mosquitoes and other biting insects. Insect repellents containing oil of lemon eucalyptus can be found in a number of different forms, ranging from the familiar insect spray to wearable bracelets. We strongly recommend sticking with insect sprays instead of wearable repellents, as it can more reliably cover vulnerable areas of your body.
Oil of lemon eucalyptus is made from the leaves of the lemon eucalyptus tree. This ingredient only became a major player in the mosquito-repelling world in 2015 when researchers did an in-depth comparison of the performance of eight commercial repellents versus non-synthetic methods. The results showed that the only plant-based spray that could compete with DEET and Picaridin’s level were options that contained Lemon Eucalyptus. Perfumes, essential oils, and vitamin B patches fell far behind.
One thing to keep in mind is that lemon eucalyptus-based sprays do fall behind when compared against highly-concentrated DEET or Picaridin sprays. In general, a repellent with 30% Lemon Eucalyptus oil performs at a similar level to a 10%-15% DEET solution. Oil of Lemon Eucalyptus also has not been thoroughly tested against mosquito species found elsewhere in the world, so this plant-based spray might not be the best choice if traveling outside the United States.
The major benefit of lemon eucalyptus-based sprays is that they are based on natural resources, which mean there have been no reports of adverse effects from proper use. There have been practically no reports on skin irritation. Oil of lemon eucalyptus sprays are best used as short-term repellents.
Oil of Lemon Eucalyptus can cause significant eye irritation. Make sure to wash your eyes out if a little of the spray mist gets into your eyes!
IR3535
IR3535, which is short for Insect Repellent 3535, is a synthetic repellent that was originally created by Merck in the 1980s. IR3535 functions by befuddling an insect’s sense of smell, which allows people to pass by undetected by biting insects such as mosquitoes or fleas.
IR3535 has been used over three decades in various commercial products. It has an excellent track record in terms of safety, where most people report no discomfort at all. Studies have also shown that IR3535 is unlikely to have long-term risks for people and is safe for the environment.
When pitted head-to-head against DEET, IR3535 saw very similar results against most insects. The area where DEET excels versus IR3535 is against mosquitos found in sub-Saharan Africa, which tend to carry diseases such as malaria, encephalitis, and dengue fever.
When pitted head-to-head against Picaridin, IR3535 also saw similar performance. There were no specific species of mosquito that one active ingredient trumped the other.
IR3535 irritates the eyes if it gets in. Fortunately, IR3535 has almost no reports of skin irritation.
Beware “Natural” Repellents
Most natural insect repellents, which typically contain plant oils such as cedar, lemongrass, rosemary, or citronella, claim that their solution can keep away mosquitos. Our tests and findings by both the CDC and EPA dispute that fact — the only reliable, proven active ingredients are the four listed above.
Number of Active Ingredients Matter
The number of active ingredients in a bug spray can make a great difference. There is such a thing as having too little or too much, which is especially true for DEET-based repellents. While both EPA and CDC have asserted that DEET is safe, repellents that have a high concentration of DEET has been reported to cause side effects such as nausea or skin rash from overexposure. Unless you have already been using DEET for a while and are confident that you will have no reaction from higher concentrations, it’s best to start with DEET sprays ranging from 20 to 50 percent.
The concentration of active ingredients influence both the efficacy of the repellent and also how long it lasts. Here’s a quick breakdown on what the numbers look like.
| Active Ingredient | Concentration | Hours of Protection |
| DEET | 5% – 10% | 2 – 4 hours |
| DEET | 15% | 6 hours |
| DEET | 25% – 30% | 8+ hours |
| Picaridin | 20% | 8+ hours |
| Oil of Lemon Eucalyptus | 30% | 5-7 hours |
| IR3535 | 20% | 7-10 hours |
Another thing to keep in mind is that some active ingredients have a strong smell. DEET, in particular, does not have the most pleasant of smells – which means higher concentration repellents will smell stronger of DEET. With DEET options higher than 30%, the smell was immediately obvious as soon as it was sprayed.
On the other hand, Picaridin is a compound that smells far less intense than DEET does. In fact, it often has barely any scent, which means the sprays can smell much better when applied. Throughout our testing, we found that Picaridin-based repellents tended to smell floral and were far more pleasant.
Things to Keep in Mind
There are a huge variety of insect repellents — and here are a few things to keep in mind when taking a look at any option.
Stay Away from “Natural” Repellents. They don’t work as well as any of the CDC and EPA-proven solutions listed above. The only natural repellent to buy are options based on Oil of Lemon Eucalyptus.
Don’t just look at active ingredient or concentration. It’s the combination of concentration and active ingredient that makes the magic happen. However, there are other factors to consider like “stickiness” of the repellent or how repulsive (or pleasant) it might smell.
Combination sunscreen & insect repellent options are no good. Sunscreens typically have to be reapplied every few hours while insect repellents last far longer. It exposes users to too much of the chemicals in insect repellents or sunburn if they opt to apply the combined solution less often.
Other Forms of Mosquito Repellents
Checkout our analysis of the claims behind other forms of mosquito repellents: