JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
METHODS
A variety of topical insect repellents and insecticides have been approved for personal protection against mosquito bites,but not all of these agents offer the same degrees of repelling efficacy and duration of protection. Insect repellents are all synthetic or plant-derived, volatile chemical substances that cause insects to move in the opposite direction from repellent- applied skin areas.³ Human hosts, however, will continue to attract mosquitoes even after repellents are applied for several reasons.³ Some of the major reasons for mosquito attraction to humans include body temperature, exhaled carbon dioxide, and clothing colors. As female mosquitoes approach humans to take blood meals, they will reach the gaseous repellent barrier that extends a few centimeters above the skin.³ The repellent barrier will lose its efficacy over time as a result of percutaneous absorption, evaporation, rubbing, sweating, and bathing or swimming.³ All insect repellents, therefore, have measurable attraction and repelling rates that are dependent on their gaseous barriers.³ All repellents also have durations of efficacy that are measured in hours.³ Unlike insect repellents,
In order to select the best combinations of topical mosquito repellents to prevent Zika virus disease and to recommend the best application methods for combining topical repellents and insecticides, a descriptive analysis of scientific articles on the efficacy and toxicity of mosquito repellents was conducted using internet search engines including Google, Google Scholar, Pub Med, Medline, and Ovid. Inclusion criteria for analysis included peer-reviewed randomized controlled trials, meta-analyses, case-control studies, case series and reports, and toxicological studies, especially those studies comparing efficacies of repellents against Aedes species mosquitoes rather than other species of mosquitoes and arthropods. Exclusion criteria included non-peer-reviewed articles, expert-opinion articles, and editorials. Since this study analyzed prior published data, institutional review board approval was not required.
RESULTS
Table 1
Insect Repellents
Formulations Strengths (%)
Efficacy Periods against Culicine
Safety in children Safety in pregnancy (FDA Pregnancy Category)
Adverse effects
Comments
Insect repellents (chemical names)
(flavivirus-carrying) mosquitos (Hours)
DEET crosses the placenta. (FDA Pregnancy Category N.)
DEET (N, N-diethyl-3-methyl- benzamide. Formerly N , N -diethyl- m -toluamide)
(5-100%)
5-10
FDA: Do not use in children under 2 months of age.
Potential neurotoxicity if applied under sunscreen.
FDA: Sunscreen that contains DEET are not recommended. May damage plastic and some synthetic fabric clothing. Safe for cotton, wool, and nylon.
Potential neurotoxicity in children if ingested or if over-applied. AAP recommends maximum strength of 30%. No studies in children, but manufacturers do not recommend use in children younger than 2 years of age. No developmental toxicity in animals.
No damage to plastics or clothing.
Picaridin (2-(2- hydroxyethyl)-1-
FDA Pregnancy Category N.
Possible skin irritation.
(7-20%)
6-8
piperidine-carboxylic acid 1-methylpropyl- ester)
FDA Pregnancy Category B.
May damage plastic and clothing.
Causes eye irritation. Potential toxicity if ingested or inhaled.
IR3535 (3-[N-butyl-N-acetyl]- amino-propionic acid ethyl ester)
(7.5-19.7%)
2-8
FDA Pregnancy Category N.
May cause seizures or death if ingested. FDA: do not use under age 3 years.
Potential skin irritation in atopic individuals.
Not very effective.
Oil of lemon eucalyptus (p-menthane-3, 8-diol)
2-6
(10-40%)
Insecticides
FDA Pregnancy Category B.
Not useful on the skin. Possible skin irritation.
A pyrethroid insecticide derived from dried, crushed flowers of Chrysan- themum . CDC: After several washings permethrin should be reapplied following label instructions.
Permethrin (3- phenoxybenzyl (1RS)- cis, trans -3-(2, 2-dichlorovinyl)-2, 2-dimethyl-cyclo- propane-carboxylate)
Sawyer Products: 6 weeks
Potential neurotoxicity if ingested or inhaled. FDA: do not use in children under age 2 years.
(0.5%)
Potential neurotoxici- ty if ingested repeatedly or over-applied.
No damage to plastics or clothing.
Pyrethroid resistance is now developing in mosquitoes.
Table 1. Available Repellents to Prevent Aedes Mosquito Bitesāµ
120 La State Med Soc VOL 170 JULY/AUG 2018
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