Insect repellent

Mosquito on a bottle of herbal mosquito repellent.

An insect repellent is a substance applied to skin, clothing, or other surfaces which discourages insects (and arthropods in general) from landing or climbing on that surface. There are also insect repellent products available based on sound production, particularly ultrasound (inaudibly high frequency sounds). These electronic devices have been shown to have no effect as a mosquito repellent by studies done by the EPA and many universities.^[1]

Insect repellents help prevent and control the outbreak of insect-borne diseases such as malaria, Lyme disease, dengue fever, bubonic plague, and West Nile fever. Pest animals commonly serving as vectors for disease include the insects flea, fly, and mosquito; and the arachnid tick.

Common insect repellents

• DEET (N,N-diethyl-m-toluamide)
• Essential oil of the lemon eucalyptus (Corymbia citriodora) and its active compound p-menthane-3,8-diol (PMD)
• Icaridin, also known as picaridin, Bayrepel, and KBR 3023
• Nepetalactone, also known as "catnip oil"
• Citronella oil^[2]
• Permethrin
• Neem oil
• Bog Myrtle
• IR3535 (3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester)

Permethrin is different in that it is actually a contact insecticide.

Repellent effectiveness

A popular post-WWII Australian brand of insect repellent.

Synthetic repellents tend to be more effective and/or longer lasting than "natural" repellents.^[3][4] In comparative studies, IR3535 was as effective or better than DEET in protection against mosquitoes.^[5] However, some plant-based repellents may provide effective relief as well.^[3][4][6] Essential oil repellents can be short-lived in their effectiveness, since essential oils can evaporate completely.

A test of various insect repellents by an independent consumer organization found that repellents containing DEET or picaridin 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.^[7]

For protection against mosquitos, the U.S. Centers for Disease Control issued a statement in May 2008 recommending equally DEET, picaridin, oil of lemon eucalyptus and IR3535 for skin.^[8] Permethrin is recommended for clothing, gear, or bed nets.^[3] 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.^[9] 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.^[10] Research has also found that neem oil is mosquito repellent for up to 12 hours.^[6] Citronella oil's mosquito repellency has also been verified by research,^[11] including effectiveness in repelling Aedes aegypti,^[12][13] but requires reapplication after 30 to 60 minutes.

Repellent safety

DEET

Icaridin

p-Menthane-3,8-diol (PMD)

Regarding safety with insect repellent use on children and pregnant women:

• Children may be at greater risk for adverse reactions to repellents, in part, because their exposure may be greater.
• Keep repellents out of the reach of children.
• Do not allow children to apply repellents to themselves.
• Use only small amounts of repellent on children.
• Do not apply repellents to the hands of young children because this may result in accidental eye contact or ingestion.
• Try to reduce the use of repellents by dressing children in long sleeves and long pants tucked into boots or socks whenever possible. Use netting over strollers, playpens, etc.
• As with chemical exposures in general, pregnant women should take care to avoid exposures to repellents when practical, as the fetus may be vulnerable.

Regardless of which repellent product used, it is recommended to read the label before use and carefully follow directions.^[14] Usage instructions for repellents vary from country to country. Some insect repellents are not recommended for use on younger children.^[8]

In the DEET Reregistration Eligibility Decision (RED) the United States Environmental Protection Agency‎ (EPA) reported 14 to 46 cases of potential DEET associated seizures, including 4 deaths. The EPA states: "... it does appear that some cases are likely related to DEET toxicity," but observed that with 30% of the US population using DEET, the likely seizure rate is only about one per 100 million users.^[15]

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".^[16]

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.^[2] Canadian regulatory authorities concern with citronella based repellents is primarily based on data-gaps in toxicology, not on incidents.^[17][18]

Within countries of the European Union, implementation of Regulation 98/8/EC,^[19] 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 (3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester) and Citriodiol (p-menthane-3,8-diol) are available. Most "natural" insect repellents such as citronella, neem oil, and herbal extracts are no longer permitted for sale as insect repellents in the EU; this does not preclude them from being sold for other purposes, as long as the label does not indicate they are a biocide (insect repellent).

Insect repellents from natural sources

There are many preparations from naturally occurring sources that are repellent to certain insects. Some of these act as insecticides while others are only repellent.

• Achillea alpina (mosquitos)
• alpha-terpinene (mosquitos)^[20]
• Basil^[21]
  • Sweet Basil (Ocimum basilicum)
• Callicarpa americana (Beautyberry)^[22]
• Camphor (moths)^[23]
• Carvacrol (mosquitos)^[20]
• Castor oil (Ricinus communis) (mosquitos)^[24]
• Catnip oil (Nepeta species) (nepetalactone against mosquitos)^[25]
• Cedar oil (mosquitos, moths)^[24]
• Celery extract (Apium graveolens) (mosquitos)^[20] In clinical testing an extract of celery was demonstrated to be at least equally effective to 25% DEET,^[26] although the commercial availability of such an extract is not known.
• Cinnamon^[27] (leaf oil kills mosquito larvae)^[28]
• Citronella oil (repels mosquitos)^[24]
• Oil of cloves (mosquitos)^[24]
• Eucalyptus oil (70%+ eucalyptol), (cineol is a synonym), mosquitos, flies, dust mites^[29])
• Fennel oil (Foeniculum vulgare) (mosquitos)^[20]
• Garlic (Allium sativum) (rice weevil, wheat flour beetle)^[30]
• Geranium oil (also known as Pelargonium graveolens)^[31][24]
• Lavender (repels insects) ^[32][33]
• Lemon eucalyptus (Corymbia citriodora) essential oil and its active ingredient p-menthane-3,8-diol (PMD)
• Lemongrass oil (Cymbopogon species) (mosquitos)^[24]
  • East-Indian Lemon Grass (Cymbopogon flexuosus)^[34]
• Marigolds (Tagetes species)
• Marjoram (Spider mites Tetranychus urticae and Eutetranychus orientalis)^[35]
• Neem oil (Azadirachta indica) (Repels or kills mosquitos, their larvae and a plethora of other insects including those in agriculture)
• Oleic acid, repels bees and ants by simulating the "Smell of death" produced by their decomposing corpses. It is a 400 millions years old natural mechanisms helping to sanitise the hives or to escape predators^[36]
• Pennyroyal (Mentha pulegium) (mosquitos,^[29] fleas^[37]), but very toxic to pets.^[37]
• Peppermint (Mentha x piperita) (mosquitos)^[38]
• Pyrethrum (from Chrysanthemum species, particularly C. cinerariifolium and C. coccineum)
• Rosemary (Rosmarinus officinalis)^[35] (mosquitos)^[24]
• Spanish Flag (Lantana camara) (against Tea Mosquito Bug, Helopeltis theivora)^[39]
• Tea tree oil^[40]
• Thyme (Thymus species) (mosquitos)^[20]
• Yellow Nightshade (Solanum villosum), berry juice (against Stegomyia aegypti mosquitos)^[41]
• Andrographis paniculata extracts(mosquito) ^[42]

Inactive substances – carriers

In 2002, the New England Journal of Medicine^[43] published an article that found products containing essential oils such as catnip^[44] or geranium oil, when combined with a suitable carrier oil such as soybean, have been found to be effective as natural repellents. This was based on testing done by Johns Hopkins^[45] and Cornell Universities.^[46] Other commercial products offered for household mosquito "control" include small electrical mats, mosquito repellent vapor, DEET-impregnated wrist bands, and mosquito coils containing a form of the chemical allethrin. Mosquito-repellent candles containing citronella oil are sold widely in the U.S. These have been used with mixed reports of success and failure.^[47]

Less effective methods

Some old studies suggested that the ingestion of large doses of thiamin could be effective as an oral insect repellent against mosquito bites. However, there is now conclusive evidence that thiamin has no efficacy against mosquito bites. ^{[48][49][50][51]} Some claim that plants like wormwood or sagewort, lemon balm, lemon grass, lemon thyme and the mosquito plant (Pelargonium) will act against mosquitoes. However, scientists have determined that these plants are “effective” for a limited time only when the leaves are crushed and applied directly to the skin.^[52]

There are several, widespread, unproven theories about mosquito control, such as the assertion that vitamin B, in particular B₁ (thiamine), garlic, ultrasonic devices or incense can be used to repel or control mosquitoes.^[53][49] Moreover, some manufacturers of "mosquito repelling" ultrasonic devices have been found to be fraudulent,^[54] and their devices were deemed "useless" in tests by the UK Consumer magazine Which?,^[55] and according to a review of scientific studies.^[56]

See also

• Mosquito net
• Pest control
• RID Insect Repellent
• Slug tape

References

1. ^ "Mosquito repellents that emit high-pitched sounds don't prevent bites" (Press release). Eurekalert!. April 17, 2007. http://www.eurekalert.org/pub_releases/2007-04/jws-mrt041607.php. 
2. ^ ^{a b} "Citronella (Oil of Citronella) (021901) Fact Sheet". United States Environmental Protection Agency. 16 February 2011. http://www.epa.gov/oppbppd1/biopesticides/ingredients/factsheets/factsheet_021901.htm. Retrieved 1 July 2011. 
3. ^ ^{a b c} M. S. Fradin and J. F. Day (2002). "Comparative Efficacy of Insect Repellents against Mosquito Bites". N Engl J Med 347 (1): 13–18. doi:10.1056/NEJMoa011699. PMID 12097535. 
4. ^ ^{a b} Collins, D.A.; Brady, J.N.; Curtis, C.F. (1993). "Assessment of the efficacy of Quwenling as a Mosquito repellent". Phytotherapy Research 7 (1): 17–20. doi:10.1002/ptr.2650070106. 
5. ^ Cilek JE, Petersen JL, Hallmon CE. (2004). "Comparative efficacy of IR3535 and deet as repellents against adult Aedes aegypti and Culex quinquefasciatus.". J Am Mosq Control Assoc 20 (3): 299–304. PMID 15532931. 
6. ^ ^{a b} Mishra AK, Singh N, Sharma VP, 1995 "Use of neem oil as a mosquito repellent in tribal villages of mandla district, madhya pradesh", Indian J Malariol, Sep;32(3):99-103 Pubmed
7. ^ "Test: Mosquito Repellents, The Verdict" Choice, The Australian Consumers Association
8. ^ ^{a b} "Updated Information regarding Insect Repellents". Centers for Disease Control and Prevention. 8 May 2008. http://www.cdc.gov/ncidod/dvbid/westnile/repellentupdates.htm. 
9. ^ "Insect Repellent Use and Safety". West Nile Virus. Centers for Disease Control and Prevention. 12 January 2007. http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm. 
10. ^ Carroll SP, Loye J, 2006, Journal of the American Mosquito Control Association 22(3):507-514, 510
11. ^ Jeong-Kyu KIM, Chang-Soo KANG, Jong-Kwon LEE, Young-Ran KIM, Hye-Yun HAN, Hwa Kyung YUN, Evaluation of Repellency Effect of Two Natural Aroma Mosquito Repellent Compounds, Citronella and Citronellal, Entomological Research 35 (2), 117–120, 2005
12. ^ Ibrahim Jantan, and Zaridah Mohd. Zaki, Development of environment-friendly insect repellents from the leaf oils of selected Malaysian plants, ASEAN Review of Biodiversity and Environmental Conservation (ARBEC), May 1998.
13. ^ Trongtokit Y, Rongsriyan Y, Komalamisra N, Apiwathnasom L, Comparative repellency of 38 essential oils against mosquito bites, Phytother Res. 2005 Apr;19(4):303-9 [1]
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16. ^ Deet
17. ^ (PDF) Re-evaluation of Citronella Oil and Related Active Compounds for Use as Personal Insect Repellents. Pest Management Regulatory Agency (Canada). 17 September 2004. ISBN 978-0-662-38012-2. Archived from the original on 2008-07-11. http://web.archive.org/web/20080711205145/http://www.pmra-arla.gc.ca/english/pdf/pacr/pacr2004-36-e.pdf. 
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26. ^ Field evaluation of G10, a celery (Apium graveolen... [Parasitol Res. 2009] - PubMed result
27. ^ Beck, Leslie. "Cinnamon — December 2006's Featured Food". http://www.lesliebeck.com/ingredient_index.php?featured_food=80. Retrieved 2007-05-01. 
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29. ^ ^{a b} "Natural Insect and Rodent Repellents - Quick & Simple". www.quickandsimple.com. http://www.quickandsimple.com/how-to/organize-clean/natural-insect-rodent-repellents. Retrieved 2009-01-02. 
30. ^ Rahman, G. K. M. M.; N. Motoyama (1998). "Identification of the active components of garlic causing repellent effect against the rice weevil and the wheat flour beetle". Nihon Oyo Doubutsu Konchu Gakkai Taikai Koen Youshi 42: 211. http://sciencelinks.jp/j-east/article/199916/000019991699A0654161.php. Retrieved 22 November 2007. 
31. ^ Botha, B. M.; C. M. McCrindle (2000). "An appropriate method for extracting the insect repellent citronellol from an indigenous plant (Pelargonium graveolens L'Her) for potential use by resource-limited animal owners". http://grande.nal.usda.gov/ibids/index.php?mode2=detail&origin=ibids_references&therow=132095. Retrieved 30 May 2009. 
32. ^ Jaenson, Thomas G. T. et al. (2006). "Repellency of Oils of Lemon Eucalyptus, Geranium, and Lavender and the Mosquito Repellent MyggA Natural to Ixodes ricinus (Acari: Ixodidae) in the Laboratory and Field". Journal of Medical Entomology 43 (4): 731–736. doi:10.1603/0022-2585(2006)43[731:ROOOLE]2.0.CO;2. ISSN 0022-2585. 
33. ^ Cook, Samantha M. et al. (2007). "Responses of Phradis parasitoids to volatiles of lavender, Lavendula angustifolia —a possible repellent for their host, Meligethes aeneus". BioControl (Springer) 52 (5): 591–598. doi:10.1007/s10526-006-9057-x. 
34. ^ Oyedele, A.O. et al. (2002). "Formulation of an effective mosquito-repellent topical product from Lemongrass oil". Phytomedicine 9 (3): 259–262. doi:10.1078/0944-7113-00120. 
35. ^ ^{a b} Momen, F. M. et al. (2001). "Repellent and Oviposition-Deterring Activity of Rosemary and Sweet Marjoram on the Spider Mites Tetranychus urticae and Eutetranychus orientalis (Acari: Tetranychidae)". Acta Phytopathologica et Entomologica Hungarica (Akadémiai Kiadó) 36 (1 – 2): 155–164. doi:10.1556/APhyt.36.2001.1-2.18. 
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39. ^ Deka, M. K. et al.. "Antifeedant and Repellent Effects of Pongam (Pongamia Pinnata) and Wild Sage (Lantana Camara) on Tea Mosquito Bug (Helopeltis Theivora)". Indian Journal of Agricultural Science 68 (5): 274. http://cat.inist.fr/?aModele=afficheN&cpsidt=10690847. Retrieved 22 November 2007. 
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48. ^ BMJ Clinical Evidence
49. ^ ^{a b} Ives A.R.; Paskewitz, S.M. (June 2005). "Testing vitamin B as a home remedy against mosquitoes". J. Am. Mosq. Control. Assoc. 21 (2): 213–217. doi:10.2987/8756-971X(2005)21[213:TVBAAH]2.0.CO;2. PMID 16033124. 
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54. ^ Lentek International-08/28/02
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External links

• Choosing and Using Insect Repellents - National Pesticide Information Center
• Alan Wood. "Insect Repellents". Compendium of Pesticide Common Names. http://www.alanwood.net/pesticides/class_insect_repellents.html. 
• Jeanie Lerche Davis (2003). "Best Insect Repellent for Mosquitoes: Bug Experts Rate Products to Keep West Nile Virus at Bay". WebMD. http://www.webmd.com/news/20030408/best-mosquito-repellent. 
• "CDC Adopts New Repellent Guidance" (Press release). Centers for Disease Control and Prevention. 28 April 2005. Archived from the original on 2008-04-30. http://web.archive.org/web/20080430220454/http://www.cdc.gov/od/oc/media/pressrel/r050428.htm. 
• Department of Health, New York State. "Health Advisory: Tick and Insect Repellents". http://www.health.ny.gov/publications/2737/. 
• Plant parts with Insect-repellent Activity from the chemical Borneol (Dr. Duke's Phytochemical and Ethnobotanical Databases)
• Mosquito repellents; Florida U