An insect repellent (also commonly called "bug spray") is a substance applied to the skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellents help prevent and control the outbreak of insect-borne (and other arthropod-bourne) diseases such as malaria, Lyme disease, dengue fever, bubonic plague, river blindness, and West Nile fever. Pest animals commonly serving as vectors for disease include insects such as flea, fly, and mosquito; and ticks (arachnids). [ citation needed ]
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.
Synthetic repellents tend to be more effective and/or longer lasting than "natural" repellents. [1] [2]
For protection against ticks and mosquito bites, the U.S. Centers for Disease Control (CDC) recommends DEET, icaridin (picaridin, KBR 3023), oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), IR3535 and 2-undecanone with the caveat that higher percentages of the active ingredient provide longer protection. [3] [4] [5]
In 2015, researchers at New Mexico State University tested 10 commercially available products for their effectiveness at repelling mosquitoes. The known active ingredients tested included DEET (at various concentrations), geraniol, p-menthane-3-8-diol (found in lemon eucalyptus oil), thiamine, and several oils (soybean, rosemary, cinnamon, lemongrass, citronella, and lemon eucalyptus). Two of the products tested were fragrances where the active ingredients were unknown. On the mosquito Aedes aegypti , the vector of Zika virus, only one repellent that did not contain DEET had a strong effect for the duration of the 240 minutes test: a lemon eucalyptus oil repellent. However, Victoria's Secret Bombshell, a perfume not advertised as an insect repellant, performed effectively during the first 120 minutes after application. [6]
In one comparative study from 2004, IR3535 was as effective or better than DEET in protection against Aedes aegypti and Culex quinquefasciatus mosquitoes. [7] Other sources (official publications of the associations of German physicians [8] as well as of German druggists [9] ) 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] [10] Essential oil repellents can be short-lived in their effectiveness. [11]
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. [12]
Although highly toxic to cats, permethrin is recommended as protection against mosquitoes for clothing, gear, or bed nets. [13] 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. [14] 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. [15] Research has also found that neem oil is mosquito repellent for up to 12 hours. [10] Citronella oil's mosquito repellency has also been verified by research, [16] including effectiveness in repelling Aedes aegypti , [17] 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. [18]
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". [19]
Regardless of which repellent product used, it is recommended to read the label before use and carefully follow directions. [20] 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 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. [21]
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". [22]
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. [23] Canadian regulatory authorities concern with citronella based repellents is primarily based on data-gaps in toxicology, not on incidents. [24] [25]
Within countries of the European Union, implementation of Regulation 98/8/EC, [26] 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 (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 due to their lack of effectiveness; 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).[ citation needed ]
A 2018 study found that Icaridin, is highly toxic to salamander larvae, in what the authors described as conservative exposure doses. [27] The LC50 standard was additionally found to be completely inadequate in the context of finding this result. [28]
Permethrin is highly toxic to cats but not to dogs or humans. [29]
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. [39]
Many other studies have also investigated the potential of natural compounds from plants as insect repellents. [40] [41] [42] Moreover, there are many preparations from naturally occurring sources that have been used as a repellent to certain insects. Some of these act as insecticides while others are only repellent. Below is a list of some natural products with repellent activity:
Some old studies suggested that the ingestion of large doses of thiamine (vitamin B1) 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. [71] [72] [73] [74] Some claim that plants such as 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. [75]
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. [72] [76] Moreover, manufacturers of "mosquito repelling" ultrasonic devices have been found to be fraudulent, [77] and their devices were deemed "useless" according to a review of scientific studies. [78]
People can reduce the number of mosquito bites they receive (to a greater or lesser degree) by:
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. [81]
Mosquitoes, the Culicidae, are a family of small flies consisting of 3,600 species. The word mosquito is Spanish and Portuguese for little fly. Mosquitoes have a slender segmented body, one pair of wings, three pairs of long hair-like legs, and specialized, highly elongated, piercing-sucking mouthparts. All mosquitoes drink nectar from flowers; females of some species have in addition adapted to drink blood. The group diversified during the Cretaceous period. Evolutionary biologists view mosquitoes as micropredators, small animals that parasitise larger ones by drinking their blood without immediately killing them. Medical parasitologists view mosquitoes instead as vectors of disease, carrying protozoan parasites or bacterial or viral pathogens from one host to another.
N,N-Diethyl-meta-toluamide, also called diethyltoluamide or DEET, is the oldest, one of the most effective and most common active ingredient in commercial insect repellents. It is a slightly yellow oil intended to be applied to the skin or to clothing and provides protection against mosquitoes, flies, ticks, fleas, chiggers, leeches, and many other biting insects.
Aedes is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except Antarctica. Some species have been spread by human activity: Aedes albopictus, a particularly invasive species, was spread to the Americas, including the United States, in the 1980s, by the used-tire trade.
Citronella oil is an essential oil obtained from the leaves and stems of different species of Cymbopogon (lemongrass). The oil is used extensively as a source of perfumery chemicals such as citronellal, citronellol, and geraniol. These chemicals find extensive use in soap, candles and incense, perfumery, cosmetic, and flavouring industries throughout the world.
Sandfly or sand fly is a colloquial name for any species or genus of flying, biting, blood-sucking dipteran (fly) encountered in sandy areas. In the United States, sandfly may refer to certain horse flies that are also known as "greenheads", or to members of the family Ceratopogonidae. The bites usually result in a small, intensely itchy bump or welt, the strength of which intensifies over a period of 5-7 days before dissipating. Moderate relief is achieved with varying success through the application of over the counter products such as Benadryl (ingested) or an analgesic cream such as After Bite. Outside the United States, sandfly may refer to members of the subfamily Phlebotominae within the Psychodidae. Biting midges (Ceratopogonidae) are sometimes called sandflies or no-see-ums. New Zealand sandflies are in the genus of sand fly Austrosimulium, a type of black fly.
Aedes aegypti, the yellow fever mosquito, is a mosquito that can spread dengue fever, chikungunya, Zika fever, Mayaro and yellow fever viruses, and other disease agents. The mosquito can be recognized by black and white markings on its legs and a marking in the form of a lyre on the upper surface of its thorax. This mosquito originated in Africa, but is now found in tropical, subtropical and temperate regions throughout the world.
Icaridin, also known as picaridin, is an insect repellent which can be used directly on skin or clothing. It has broad efficacy against various arthropods such as mosquitos, ticks, gnats, flies and fleas, and is almost colorless and odorless. A study performed in 2010 showed that picaridin spray and cream at the 20% concentration provided 12 hours of protection against ticks. Unlike DEET, icaridin does not dissolve plastics, synthetics or sealants, is odorless and non-greasy and presents a lower risk of toxicity when used with sunscreen, as it may reduce skin absorption of both compounds.
Corymbia citriodora, commonly known as lemon-scented gum and other common names, is a species of tall tree that is endemic to north-eastern Australia. It has smooth white to pink bark, narrow lance-shaped to curved adult leaves, flower buds in groups of three, white flowers and urn-shaped or barrel-shaped fruit.
Nootkatone is an organic compound, a sesquiterpenoid, which means that it is a C15 derivative that also contains an oxygen-containing functional group. It is the most valuable aroma compound of grapefruit. Nootkatone was originally isolated from the wood of the Alaskan yellow cedar, Cupressus nootkatensis. The species name, nootkatensis, is derived from the language of the Nuu-Chah-Nulth people of Canada.
Pelargonium 'citrosum' is a perennial subshrub with fragrant leaves that are reminiscent of citronella.
p-Menthane-3,8-diol, also known as para-menthane-3,8-diol, PMD, or menthoglycol, is an organic compound classified as a diol and a terpenoid. It is colorless. Its name reflects the hydrocarbon backbone, which is that of p-menthane. A total of eight stereoisomers are possible, based on the three stereocenters of the ring. Depending on the source, one or more may predominate.
Nepeta cataria, commonly known as catnip, catswort, catwort, and catmint, is a species of the genus Nepeta in the family Lamiaceae, native to southern and eastern Europe, the Middle East, Central Asia, parts of Mongolia, and parts of China. It is widely naturalized in northern Europe, New Zealand, and North America. The common name catmint can also refer to the genus as a whole.
RID is an Australian brand of personal insect repellent sold and distributed in Australia, New Zealand, and online.
Aedes triseriatus is a member of the true fly order. It is called the eastern treehole mosquito due to its predilection towards breeding in stagnant water that is found in natural holding containers such as tree holes. It is native to the eastern United States and southern Canada and favors hardwood habitats. It has been found as far south as the Florida Keys, as far west as Idaho and Utah, and as far north as Quebec and Ontario. This species has not yet been found in Europe, but it has the potential to spread through international trade. In 2004, it was found in a shipment of tires travelling from Louisiana to France, but it was identified and targeted with insecticides that truncated its spread. It is a known vector of La Crosse encephalitis and canine heartworm disease. In the laboratory, it has been found to vector several other viruses including yellow fever, eastern encephalitis, Venezuelan encephalitis, and western encephalitis. Because of its potential for international spread and its proclivity for transmitting disease, monitoring the distribution of this species is essential.
Ethyl butylacetylaminopropionate is an insect repellent whose trade name is IR3535 and was developed and commercialized by Merck KGaA (Germany). It is a colorless and odorless oil with a good skin feel in final products, and it is biodegradable.
SS220 is an insect repellent with a broad range of efficacy.
Callicarpenal is a terpenoid that has been isolated from plants of the genus Callicarpa (beautyberry). It acts as an insect repellent against mosquitoes and fire ants. It also has activity against ticks.
Anthranilate-based insect repellents include methyl anthranilate, N,N-dimethylanthranilic acid (DMA), ethyl anthranilate (EA), and butyl anthranilate (BA). Chemically, they are esters of anthranilic acid. While the United States Food and Drug Administration (FDA) has approved some of these compounds for use as food additives, cinnamyl anthranilate is banned by the FDA. The compounds repel both fruit flies and mosquitos, and target the same neurons that respond to DEET. The receptors are located on part of the antennae known as the sacculus.
Howard Carter is a British inventor and businessman. He foundered Incognito in 2007. He is an expert in the field of insects and specifically as a mosquito bite prevention expert. After contracting two life-threatening diseases from mosquito bites, despite using a high-percentage DEET-based repellent, he was motivated to invent a totally natural, equally effective mosquito repellent, incognito anti-mosquito. This was, in part, because statistics were suggesting more mosquitoes were becoming resistant to synthetic repellents that contained controversial pesticides such as DDT and DEET.
'Anything intended for topical use only shouldn't be going into the body,' says Xiaochen Gu, a professor at the University of Manitoba's faculty of pharmacy, who led the study.
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