3.4 Essential oils

have been active, whereas 25 have been canceled. These include Citriodiol, Repel essential insect repellent lotion (two variants), Repel essential insect repellent pump spray, and Repel insect repellent 30 by the United Industrial Corp., USA. Some eucalyptus-based products include the following: Quwenling is successfully

marketed as an insect repellent in China and provides protection against anopheles mosquitoes parallel to DEET and has exchanged the widely used synthetic repellent

isopulegone. Mosiguard Natural contains 50% eucalyptus oil, Buzz Away is a commercially available product in China based on citronellal, and MyggA1 Natural is based on PMD from lemon eucalyptus and is shown to repel ticks. More details are

The name "Citronella" is derived from the French word "citronelle" around 1858. It was extracted to be used in perfumery and used by the Indian Army to repel mosquitoes at the beginning of the twentieth century and was then registered for commercial use in the USA in 1948. Today, citronella (5–10%) is one of the most widely used natural repellents on the market; such concentrations are lower than most other commercial repellents, whereas higher concentrations can cause skin sensitivity. Among plant-derived substances, products containing Citriodiol showed the most effective repellent profile against mosquitoes. EOs and extracts belonging to plants in the Citronella genus (Poaceae) are commonly used as ingredients of plant-based mosquito repellents, mostly Cymbopogon nardus that is sold in Europe and North America in commercial preparations [39]. Citronella contains citronellal, citronellol, geraniol, citral, α-pinene, and limonene giving an effect similar to that of DEET, but the oils rapidly evaporate causing loss of efficacy and leaving the user unprotected. Among plant-derived substances, products containing Citriodiol showed the most effective repellent profile against mosquitoes. For travelers heading to disease-endemic areas, citronella-based repellents should not be recommended, but if efficacious alternatives are prohibitively expensive or not available, the use of citronella to prevent mosquito bites may provide important protection from disease vectors. Even though citronella-based repellents only give protection from host-seeking mosquitoes for a short time (2 h), formulations could

The aromatic plants of the Meliaceae family which include neem, Azadirachta indica, Carapa procera, Melia azedarach, Khaya senegalensis, and Trichilia emetica contain substances of the limonoid group and insecticidal and repellent effects on insects [18]. Neem provided a protection of 98.2% for 8 h against An. darlingi. Regardless of being not approved by US EPA for use as a topical insect repellent, neem is widely advertised as a natural alternative to DEET, and it has been tested for repellency against a wide range of arthropods of medical and veterinary importance. MiteStop®, based on a neem seed extract, had a considerable repellent effect on bloodsucking mosquitoes, tabanids, ceratopogonids, simuliids, as well as licking flies [41]. Several field studies from India have shown the very high efficacy of neem-based preparations, contrasting with findings of intermediate repellency by other researchers. However, these contrasting results may be due to differing

Methyl jasmonate (MJ) is derived from the nonvolatile jasmonic acid and has the ultimate vapor pressure for a repellent (0.001 mmHg at 25°C) which is quite higher

prolong such time (please see the formulation section).

methodologies and the solvents used to carry the repellents.

3.3 Neem and methyl jasmonate

152

dimethylphthalate; Quwenling contains a mixture of PMD, citronellol, and

widely discussed [40].

3.2 Citronella

Malaria

EOs are used against insects [20, 42–50] throughout the globe. EOs are distilled from members of the Lamiaceae (mint family), Poaceae (aromatic grasses), and Pinaceae (pine and cedar family). EOs could be used for farm animal protection against nuisance flies and lice [47]. Almost all of the botanical repellents are also used for food flavoring or in the perfume industry, indicating that they are safer than DEET. The most effective oils include thyme, geraniol, peppermint, cedar, patchouli, and clove that have been found to repel malaria, filarial, and yellow fever vectors for a period of 60–180 mins. Most of these EOs are highly volatile, and this contributes to their poor longevity as mosquito repellents. As a result, repellents containing only EOs in the absence of an active ingredient such as DEET should not be recommended as repellents for use in disease-endemic areas, whereas those containing high levels of EOs could cause skin irritation, especially in the presence of sunlight [39]. Although EOs effectively repel mosquitoes as irritants, repellents, antifeedants, or maskants, unfortunately, relatively few have been commercialized, despite being widely used in candles and as topical insect repellents. Botanical, herbal, or natural-based repellents include one or several plant EOs. These oils are considered safe by the EPA at low concentrations but provide a limited duration of protection against mosquitoes (<3 h). Citronella (discussed previously) is the principal and sometimes only active ingredient in many plant-based insect repellents [7]. Eucalyptus oil is used as an antifeedant mainly against biting insects as eucalyptus-based products used on humans as insect repellent can give protection from biting insects up to 8 h depending upon the concentration of the essential oil. Such repellent activity could be extended up to 8 days when eucalyptus EOs are applied on the clothes. Eucalyptus oil (30%) can prevent mosquito bite for 2 h; however, the oil must have at least 70% cineole content [40]. On the other hand, E. citriodora EO alone showed an insufficient protection against the three main mosquito species [14].
