Insect repellent
An insect repellent (also commonly called "bug spray") is a substance applied to the skin, clothing, or other surfaces to discourage
Some insect repellents are insecticides (bug killers), but most simply discourage insects and send them flying or crawling away. Nearly any would be fatal upon reaching the median lethal dose, but classification as an insecticide implies death even at lower doses.
Effectiveness
For protection against mosquito bites, the U.S.
In 2015, Researchers at
In one comparative study from 2004, IR3535 was as effective or better than DEET in protection against Aedes aegypti and Culex quinquefasciatus mosquitoes.[5] Other sources (official publications of the associations of German physicians[6] as well as of German druggists[7]) suggest the contrary and state DEET is still the most efficient substance available and the substance of choice for stays in malaria regions, while IR3535 has little effect. However, some plant-based repellents may provide effective relief as well.[1][2][8] Essential oil repellents can be short-lived in their effectiveness.[9]
A test of various insect repellents by an independent consumer organization found that repellents containing DEET or icaridin are more effective than repellents with "natural" active ingredients. All the synthetics gave almost 100% repellency for the first 2 hours, where the natural repellent products were most effective for the first 30 to 60 minutes, and required reapplication to be effective over several hours.[10]
Although highly toxic to cats, permethrin is recommended as protection against mosquitoes for clothing, gear, or bed nets.[11] In an earlier report, the CDC found oil of lemon eucalyptus to be more effective than other plant-based treatments, with a similar effectiveness to low concentrations of DEET.[12] However, a 2006 published study found in both cage and field studies that a product containing 40% oil of lemon eucalyptus was just as effective as products containing high concentrations of DEET.[13] Research has also found that neem oil is mosquito repellent for up to 12 hours.[8] Citronella oil's mosquito repellency has also been verified by research,[14] including effectiveness in repelling Aedes aegypti,[15] but requires reapplication after 30 to 60 minutes.
There are also products available based on sound production, particularly ultrasound (inaudibly high-frequency sounds) which purport to be insect repellents. However, these electronic devices have been shown to be ineffective based on studies done by the United States Environmental Protection Agency and many universities.[16]
Safety issues
For humans
Children may be at greater risk for adverse reactions to repellents, in part, because their exposure may be greater. Children can be at greater risk of accidental eye contact or ingestion. As with chemical exposures in general, pregnant women should take care to avoid exposures to repellents when practical, as the fetus may be vulnerable.
Some experts also recommend against applying chemicals such as DEET and sunscreen simultaneously since that would increase DEET penetration. Canadian researcher, Xiaochen Gu, a professor at the University of Manitoba's faculty of Pharmacy who led a study about mosquitos, advises that DEET should be applied 30 or more minutes later. Gu also recommends insect repellent sprays instead of lotions which are rubbed into the skin "forcing molecules into the skin".[17]
Regardless of which repellent product used, it is recommended to read the label before use and carefully follow directions.[18] Usage instructions for repellents vary from country to country. Some insect repellents are not recommended for use on younger children.[3]
In the DEET Reregistration Eligibility Decision (RED) the
The Pesticide Information Project of Cooperative Extension Offices of Cornell University states that, "Everglades National Park employees having extensive DEET exposure were more likely to have insomnia, mood disturbances and impaired cognitive function than were lesser exposed co-workers".[20]
The EPA states that citronella oil shows little or no toxicity and has been used as a topical insect repellent for 60 years. However, the EPA also states that citronella may irritate skin and cause dermatitis in certain individuals.[21] Canadian regulatory authorities concern with citronella based repellents is primarily based on data-gaps in toxicology, not on incidents.[22][23]
Within countries of the European Union, implementation of Regulation 98/8/EC,[24] commonly referred to as the Biocidal Products Directive, has severely limited the number and type of insect repellents available to European consumers. Only a small number of active ingredients have been supported by manufacturers in submitting dossiers to the EU Authorities.
In general, only formulations containing DEET, icaridin (sold under the trade name Saltidin and formerly known as Bayrepel or KBR3023), IR3535 and citriodiol (
Toxicity for other animals
A 2018 study found that
Permethrin is highly toxic to cats but not to dogs or humans.[27]
Common insect repellents
Common synthetic insect repellents
- Benzaldehyde, for bees[28]
- Butopyronoxyl (trade name Indalone). Widely used in a "6-2-2" mixture (60% Dimethyl phthalate, 20% Indalone, 20% Ethylhexanediol) during the 1940s and 1950s before the commercial introduction of DEET
- DEET (N,N-diethyl-m-toluamide)
- Dimethyl carbate
- Dimethyl phthalate, not as common as it once was but still occasionally an active ingredient in commercial insect repellents
- Ethyl butylacetylaminopropionate (IR3535 or 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester)
- Ethylhexanediol, also known as Rutgers 612 or "6–12 repellent," discontinued in the US in 1991 due to evidence of causing developmental defects in animals[29]
- Icaridin, also known as picaridin, Bayrepel, and KBR 3023
- Methyl anthranilate and other anthranilate-based insect repellents
- Metofluthrin
- Permethrin is a contact insecticide rather than a repellent
- SS220 is a repellent being researched that has shown promise to provide significantly better protection than DEET
- Tricyclodecenyl allyl ether, a compound often found in synthetic perfumes[30][31]
Common natural insect repellents
- Beautyberry(Callicarpa) leaves
- Birch tree bark is traditionally made into tar. Combined with another oil (e.g., fish oil) at 1/2 dilution, it is then applied to the skin for repelling mosquitos[33]
- Bog myrtle(Myrica gale)
- Catnip oil whose active compound is Nepetalactone
- Citronella oil[21] (citronella candles are not effective)[34][35]
- p-menthane-3,8-diol(PMD)
- Lemongrass
- Neem oil
- Tea tree oil[36] from the leaves of Melaleuca alternifolia
- Tobacco
Insect repellents from natural sources
Several natural ingredients are certified by the United States Environmental Protection Agency as insect repellents, namely catnip oil, oil of lemon eucalyptus (OLE) (and its active ingredient p-Menthane-3,8-diol), oil of citronella, and 2-Undecanone, which is usually produced synthetically but has also been isolated from many plant sources.[37]
Many other studies have also investigated the potential of natural compounds from plants as insect repellents.
- Achillea alpina (mosquitos)[41]
- alpha-terpinene (mosquitos)[42]
- Andrographis paniculata extracts (mosquito)[43]
- Basil[44]
- Sweet basil (Ocimum basilicum)
- Sweet basil (
- Breadfruit (Insect repellent, including mosquitoes[45])
- beautyberry)[46]
- Camphor (mosquitoes)[47]
- Carvacrol (mosquitos)[48]
- Castor oil (Ricinus communis) (mosquitos)[49]
- Catnip oil (Nepeta species) (nepetalactone against mosquitos)[50][41]
- Cedar oil (mosquitos, moths)[49]
- Celery extract (Apium graveolens) (mosquitos) In clinical testing an extract of celery was demonstrated to be at least equally effective to 25% DEET,[51] although the commercial availability of such an extract is not known.
- leaf oil kills mosquito larvae)[52]
- Citronella oil (repels mosquitos) (contains insect repelling substances, such as citronellol and geraniol)[49][41]
- Clove oil (mosquitos)[49]
- D-Limonene (ticks, fleas, flies, mosquitoes, and other insects) (widely used in insect repellents for pets)[53]
- miticide.[55]
- Fennel oil (Foeniculum vulgare) (mosquitos)[41]
- Garlic (Allium sativum) (Mosquito, rice weevil, wheat flour beetle)[56]
- Hinokitiol (ticks, mosquitos, larvae)[58][59]
- Lemon eucalyptus (Corymbia citriodora) essential oil and its active ingredient p-menthane-3,8-diol (PMD)[41]
- Lemongrass oil (Cymbopogon species) (mosquitos)[49]
- East-Indian lemon grass (Cymbopogon flexuosus)[62]
- Linalool (ticks, fleas, mites, mosquitoes, spiders, cockroach)[63]
- Marjoram (spider mites Tetranychus urticae and Eutetranychus orientalis)[64]
- Mint (menthol is active chemical.) (Mentha sp.)
- Neem oil (Azadirachta indica) (Repels or kills mosquitos, their larvae and a plethora of other insects including those in agriculture)[41]
- Nootkatone (ticks, mosquitoes and other insects)[65]
- smell of death" produced by their decomposing corpses.
- Pennyroyal (Mentha pulegium) (mosquitos, fleas,) but very toxic to pets
- Peppermint (Mentha x piperita) (mosquitos)[66]
- Pyrethrum (from Chrysanthemum species, particularly C. cinerariifolium and C. coccineum)[41][67]
- Rosemary (Rosmarinus officinalis)[64] (mosquitos)[49]
- Spanish Flag (Lantana camara) (against Tea Mosquito Bug, Helopeltis theivora)[68]
- Tea tree oil[36] from the leaves of Melaleuca alternifolia
- Thyme (Thymus species) (mosquitos)[41]
- Yellow nightshade (Stegomyia aegyptimosquitos)
Less effective methods
Some old studies suggested that the ingestion of large doses of
There are several, widespread, unproven theories about
Alternatives to repellent
People can reduce the number of mosquito bites they receive (to a greater or lesser degree) by:
- Using a mosquito net
- Wearing long clothing that covers the skin and is tucked in to seal up holes[77]
- Avoiding the outdoors during dawn and dusk, when mosquitos are most active[77]
- Keeping air moving to prevent mosquitos from landing, such as by using a fan[77]
- Wearing light-colored clothing (light objects are harder for mosquitos to detect)[78]
- Reducing exercise, which reduces output of carbon dioxide used by mosquitos for detection[78]
History
Testing and scientific certainty were desired at the end of the 1940s. To that end products meant to be used by humans were tested with model animals to speed trials. Eddy & McGregor 1949 and Wiesmann & Lotmar 1949 used mice, Wasicky et al. 1949 canaries and guinea pigs, Kasman et al. 1953 also guinea pigs, Starnes & Granett 1953 rabbits, and many used cattle.[79]
See also
- Fly spray (insecticide)
- Mosquito coil
- Mosquito control
- Mosquito net
- Pest control
- RID Insect Repellent
- Slug tape
- VUAA1
- Chemical ecology
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- ^ Are Citronella Candles an Effective Mosquito Repellent?
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External links
- 2011 review of studies of plant-based mosquito repellents – NIH
- Aphid repellents Archived 2014-04-20 at the Wayback Machine
- Choosing and Using Insect Repellents – National Pesticide Information Center
- Davis JL (2003). "Best Insect Repellent for Mosquitoes: Bug Experts Rate Products to Keep West Nile Virus at Bay". WebMD.
- "CDC Adopts New Repellent Guidance" (Press release). Centers for Disease Control and Prevention. 28 April 2005. Archived from the original on 2008-04-30.
- Department of Health, New York State. "Health Advisory: Tick and Insect Repellents". Archived from the original on 2010-11-21. Retrieved 2011-01-05.
- Dr. Duke's Phytochemical and Ethnobotanical Databases[permanent dead link] (plant parts with Insect-repellent Activity from the chemical Borneol)
- Mosquito repellents; Florida U
- Insect repellent active ingredients recommended by the CDC