Reviews
Insect repellents: An updated review for the clinician

https://doi.org/10.1016/j.jaad.2018.10.053Get rights and content

Malaria, Zika virus, West Nile virus, Dengue fever, and Lyme disease are common causes of morbidity and mortality around the world. While arthropod bites may cause local inflammation and discomfort, a greater concern is the potential to develop deadly systemic infection. The use of insect repellents (IRs) to prevent systemic infections constitutes a fundamental public health effort. Cost effectiveness, availability, and high efficacy against arthropod vectors are key characteristics of an ideal IR. Currently, numerous IRs are available on the market, with N,N-diethyl-3-methylbenzamide (DEET) being the most widely used. DEET has an excellent safety profile and remarkable protection against mosquitoes and various other arthropods. Other Environmental Protection Agency–registered IR ingredients (eg, permethrin, picaridin, IR3535, oil of lemon eucalyptus, oil of citronella, catnip oil, and 2-undecanone) are alternative IRs of great interest because some of these ingredients have efficacies comparable to that of DEET. These alternative IRs possess low toxicity and favorable customer experiences in use (eg, cosmetically pleasant, naturally occurring). This review summarizes the currently available Environmental Protection Agency–registered IRs, including their origins, mechanisms of action, side effect profiles, and available formulations. This review will enable the clinician to select the best IR option to meet a patient’s needs and provide the greatest protection from arthropod bites and their sequelae.

Section snippets

N,N-diethyl-3-methylbenzamide

N,N-diethyl-3-methylbenzamide (DEET) has been considered the most broad-spectrum, efficacious IR since the 1950s, and is currently used by 50 to 100 million individuals in the United States annually. Originally created by the US Army, DEET was made commercially available in 1956. Currently, there are >200 DEET products available on the market, ranging from concentrations of 5% to 100%.8 In the majority of circumstances, concentrations of 10% to 35% will enable adequate protection, with efficacy

Natural compounds

Natural compounds are a category of IRs approved by the FDA that encompass a variety of essential plant oils, or their active compounds, that act as the main active ingredient. These natural products are generally safer for human use compared with synthetic nonbiodegradable products, such as DEET.63, 64, 65 The list of plant-derived IRs are numerous. In this section, we focus on the EPA-registered natural compound IRs.

Permethrin

Permethrin is a pyrethrin, and pyrethrins are extracts of the chrysanthemum flower. Permethrin should not be applied directly to the skin.88 This product is intended to be used only to treat clothing, and represents the only IR currently registered to treat fabric in the United States.89 First marketed in 1973, permethrin acts as an IR and insecticide that is highly effective against mosquitoes, ticks, and flies equally,53 and has even been shown to repel ticks more effectively than DEET.90

Uncited Table

Table I.

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  • Cited by (29)

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      IR3535® is a synthetic compound based on the amino acid alanine, approved by the Food and Drug Administration (FDA) in 1999. It is a colorless, relatively odorless, and biodegradable material, and its formulations are applicable in concentrations of 7.5–19.7% to aerosols, lotions, pump sprays, and wipes among others [6]. IR3535® has low levels of toxicity and is prescribed for pregnant women and babies aged over 6 months; thus, it is considered to be the most suitable option among synthetic insect repellents [1].

    • Repellent and acaricidal activity of coconut oil fatty acids and their derivative compounds and catnip oil against Amblyomma sculptum

      2021, Veterinary Parasitology
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      The 7-day repellency was previously reported by Zhu et al. (2018) while tested against another tick species, R. sanguineus s.l. from coconut oil fatty acids. Catnip oil is known to repel various blood-sucking insects including biting flies, mosquitoes and ticks, but with a relatively shorter effective period (< 24 h) (Nguyen et al., 2018; Zhu et al., 2014). It is somewhat surprising the 4-day long effectiveness in repellency observed in the present study against A. sculptum.

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    Funding sources: None.

    Conflicts of interest: None disclosed.

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