Insect repellents are used to repel mosquitoes, ticks, flies, and other biting insects. Mosquitoes can transmit diseases such as Zika, Malaria, and West Nile virus. Ticks can transmit Lyme disease, Rocky Mountain Spotted Fever, and other diseases. Repellents are not meant to kill insects, but to keep them away to prevent bites and the spread of disease.
There are multiple active ingredients in insect repellents registered with the Environmental Protection Agency (EPA). DEET, picaridin, IR3535, and oil of lemon eucalyptus are referred to in this fact sheet as common insect repellents. The Centers for Disease Control and Prevention (CDC) recommends using products with one of these EPA registered ingredients. They can be applied to human skin and some can be used on clothing. They come as sprays, wipes, or lotions. Find the repellent that is best for you with EPA's repellent search tool.
Oil of lemon eucalyptus and IR3535 are based off of chemicals that occur in nature but are man-made ingredients. Because they are related to substances found in nature, they are both considered to be biopesticides. Oil of lemon eucalyptus (OLE) may also be listed on products by its chemical name, p-menthane-3,8-diol (PMD).
Mosquitoes and ticks are attracted to skin odors and the carbon dioxide we exhale. They also use heat, movement, and visual cues to find a possible host.1,2 Repellents affect an insect's senses such as smell and taste to prevent it from finding a human or animal host.2,3,4
Length of protection and efficacy of repellents can vary. They must undergo testing to show they are effective before they can claim to control mosquitoes or ticks. Look for label claims on your repellents. The CDC recommends using products that are registered with the EPA.
Higher concentration repellents may protect people for longer. However, they are not better at keeping insects away.5,6,7 Repellents with less than 10% of an active ingredient may only offer protection for short periods of time (1-2 hours).5 Sweat, water contact, and rubbing from clothing can affect how long a repellent may be effective.6,7,8 Water resistant repellents are available.
If you choose to use a DEET product, the CDC recommends products with DEET concentrations of 20% or more.9 Products with more than 50% DEET offer no extra protection.5,10 Consider using a variety of methods to prevent bites. You may cover exposed skin with clothing or alter the landscaping in your yard to make it less tick or mosquito friendly.
All chemicals, including insect repellents, have some degree of toxicity. However, the toxicity can vary by product and by route of exposure (eating, breathing, touching). Each product is also marked with a signal word. This indicates the toxicity of the whole mixture.
Applications to skin are the most common use of repellents. They are low or very low in toxicity when used on the skin. Inhalation is possible when using a spray. If hands are not washed after use, residues could be eaten by mistake. Consider taking steps to avoid exposures in the ears, eyes, and mouth. You can also keep the risk low by following the label directions. Tables 1 and 2 below can be used to compare the toxicity of different ingredients in repellents.
Table 1. Short-Term Toxicity of Active Ingredients in Common Insect Repellents*
|Repellent||Oral||Inhalation||Dermal||Eye Irritation||Skin Irritation|
|DEET11||Low||Very low||Low||Low||Very low|
|Picaridin12||Low||Very low||Low||Low||Very low|
|IR353513||Very Low||Very low||Very Low||Moderate||Very low|
|Oil of Lemon Eucalyptus14||Very Low||Very low||Very Low||High**||Very low|
* None of these ingredients are expected to cause more severe reactions with multiple exposures over time (sensitizers).
** If oil of lemon eucalyptus gets into the eye, washing the eye immediately can reduce irritation and risk of long-term damage. Follow First Aid instructions on the product label.
Table 2. Short-Term Toxicity of Insecticide Active Ingredient Used to Treat Clothing
|Insecticide||Oral||Inhalation||Dermal||Eye Irritation||Skin Irritation|
|Permethrin15||Low||No Acceptable Data||Low||Low||Very low|
Permethrin is not an insect repellent, but kills insects on contact. It is sometimes used to treat fabrics. For additional information about permethrin-treated fabrics, see below.
DEET: While uncommon, products with DEET can cause short-term eye or skin irritation.16 People who have inhaled DEET repellents have reported coughing and respiratory irritation. If eaten, they can cause stomach and digestive irritation. Although rare and largely due to accidents or overexposures, neurological effects have been reported. The EPA found inconclusive evidence linking seizures in children to DEET exposure.11
Oil of lemon eucalyptus: Oil of lemon eucalyptus can cause significant eye damage. Washing eyes after an exposure can reduce the risks of long-term harm. It has been linked to skin irritation in animal studies. Rats fed oil of lemon eucalyptus had trouble walking. They also had changes in their breathing and were lethargic.14
If you or someone you know is having a reaction to an insect repellent, carefully follow the First Aid instructions on the product label. For more advice, contact the Poison Control Center at 800-222-1222.
Repellents are often used for a few days or weeks. However, various jobs and other conditions may result in daily use of a repellent for extended periods. In a few studies, animals were treated with common repellents every day for long periods of time. They sometimes had irritated skin. Symptoms were limited to skin irritation and did not include other systemic effects.12,14,16,19,20
Agencies use many studies to find links between certain substances and cancer. The EPA lists the ingredient DEET as "not classifiable as to human carcinogenicity."21 This indicates that data has not been conclusive enough to state if it is or is not likely to cause cancer.
Other common repellent active ingredients have not had full assessments done to determine the cancer risks. However, one of the signs that a chemical could be linked to cancer is if it affects genes or cell DNA in a lab. None of the common repellent ingredients have been shown to damage genes in lab tests.11,12,22,23
Repellents have been tested and designed for use in certain ways. Only use a repellent in ways that are described on the label. Following the label directions and the tips below can minimize your risk.
Children may be more likely to mishandle a bottle or lick treated skin, increasing their risks. Check the product label to see if there is a minimum age for use. If no age limit is on the label, the EPA has not put age restrictions on the product. Here are a few tips from professional organizations:
Take precautionary steps to reduce a child's contact with a repellent:
According to the CDC, EPA-registered repellents may be used during pregnancy and while breastfeeding.9 Repellents may reduce risks from insect-spread diseases that could affect a developing baby. The American College of Obstetricians and Gynecologists (ACOG) recommends use of an EPA-registered repellent with DEET for pregnant mothers in areas with risk of Zika.28 Consult a healthcare professional for more information.
There is currently no published data on the use of common repellents while breastfeeding.29,30,31,32 The CDC has indicated that use of EPA-registered insect repellents while breastfeeding is low risk. The World Health Organization (WHO) has listed DEET as “compatible with breastfeeding” when used as directed.33
DEET: No harmful effects were seen in mothers or their infants that regularly applied DEET products during their second and third trimesters of pregnancy.34 Inhalation, dermal, and feeding studies with animals show the ingredient DEET is low in developmental and reproductive toxicity. Inhalation and feeding studies showed no effect on animal reproductive organs.16
Picaridin: No effects on pregnancies or fetuses were found in studies when animals were fed or had their skin treated with concentrated picaridin before or during pregnancies.12,35
IR3535: Multiple feeding studies show concentrated IR3535 is low in developmental and reproductive toxicity.19,22 There is some evidence of dose-related pregnancy loss in animals fed large doses while pregnant.22
Oil of lemon eucalyptus: Only slight changes in weight gain were observed during pregnancy in rats with large doses of the ingredient put on their skin. There were no effects on fetal development.14
When a repellent is applied to skin, about 3-19% may be absorbed into the body.12,20,36,37,38 Mixing an insect repellent with sunscreen can affect how your skin absorbs both products.8,24 Using both can increase repellent absorption through skin. However, the effects of using both depend on which sunscreen and which repellent is used. Few or no studies address using IR3535 or oil of lemon eucalyptus with sunscreens.
The CDC does not recommend products that have both sunscreen and an insect repellent.26 Many repellents work for many hours. Sunscreen may need to be used more often than a repellent. Therefore, combined products may not be used as often as they should be for sun protection. If you decide to use both, the CDC recommends applying sunscreen first, letting it dry, and then applying an insect repellent over the sunscreen.26
Water from washing clothing and bathing is treated at a nearby wastewater treatment plant.39 Repellents are not on the EPA's list of contaminants that must be monitored by public water systems.40 State and local regulations may vary. Consider contacting a local water treatment facility for information about water quality in your area.
Repellents may also be washed off of skin and clothing into lakes or rivers during recreation. A repellent will tend to travel with water if it is dissolved. It could travel either downstream or through soil. The solubilities of DEET and picaridin are variable.41,42 IR3535 is soluble in water and dissolves easily.19 Oil of lemon eucalyptus is moderately soluble.14 DEET, picaridin, and IR3535 are mobile or moderately mobile in soils. They are not likely to stick to soil.18,41,42
The breakdown of repellents in air, water, and soils has not been widely studied. Reports for breakdown times of picaridin and DEET in soil or water are variable and range from days to weeks, or longer.35,42,43,44
As for their movement in the environment, the four repellents are moderately volatile and can release vapors into the air.14,19,41,42 Once in the air, DEET, picaridin, and IR3535 do not stay there for long. Their half-lives in air range between 7 and 15 hours.17,18,42
DEET is slightly toxic to birds, fish, and aquatic invertebrates.42 Picaridin is practically non-toxic to birds, fish, and aquatic invertebrates.41 Few studies on the toxicity of IR3535 and oil of lemon eucalyptus to birds and fish are available. Scientists have not found effects on small organisms such as snails, mayflies, or water fleas from small amounts of DEET, picaridin, or IR3535 in natural waters.45,46,47
The health risks and efficacy of essential oils have not been as widely studied as common insect repellents. However, a variety of information is available, including information from CDC.48 Some of these other repellents may be minimum risk pesticides and may not have to be registered with the EPA. There are no EPA-registered repellents that contain garlic oil, rosemary, lemongrass, thyme, or geraniol oils as active ingredients.
Do not apply permethrin to skin as a repellent. There are some products with permethrin that can be used to treat fabrics. Permethrin works on contact, meaning that an insect must touch the treated item to be harmed or killed.49 Exposure to permethrin while wearing treated clothing is likely to be low because only a very small amount of product may be transferred onto skin from treated fabric.15,50 Additionally, skin absorption of permethrin is low.15
Do not apply permethrin to clothing while it is being worn. Only treat clothing, netting, or gear with products that have specific directions for treating fabrics. Do not over-treat fabrics. Use the correct concentration for treatment. Allow any treated items to dry thoroughly after treatment before handling or wearing.
For more detailed information about insect repellents please visit the list of referenced resources, call the National Pesticide Information Center, Monday - Friday, between 8:00am - 12:00pm Pacific Time (11:00am - 3:00pm Eastern Time) at 800-858-7378, or visit us on the web at npic.orst.edu. NPIC provides objective, science-based answers to questions about pesticides.
Please cite as: Strid, A.; Hanson, W.; Cross, A.; Bond, C.; Jenkins, J. 2018. Insect Repellents Fact Sheet; National Pesticide Information Center, Oregon State University Extension Services. http://npic.orst.edu/factsheets/repellents.html.
NPIC fact sheets are designed to answer questions that are commonly asked by the general public about pesticides that are regulated by the U.S. Environmental Protection Agency (U.S. EPA). This document is intended to be educational in nature and helpful to consumers for making decisions about pesticide use.