Essential oils as Insect Repellent Agent
Insect repellents are known as an agent used to make insects or bugs do not bite human skin to reduce the risk of local and systemic effects, including insect-borne disease i.e. malaria, zika virus, West Nile virus, dengue fever, yellow fever, and chikungunya fever. Insect repellents work by creating a vapor barrier that prevents insects coming to the human skin [1].
Do you know that mosquitoes can detect odorant-binding proteins (OBPs), protein that are released by human skin, and use it as signals as a time to bite you?
Mosquitoes are also attracted by the carbon dioxide that humans release. With insect repellent, it affects insect’s sense such as smell and taste to prevent it from finding human or animal host [2].
Plant-derived insect repellent is now gaining much interest aside of using chemical insect repellent because of its safety, such as permethrin from chrysanthemum flower, para-menthane3,8-diol derived from lemon eucalyptus oil, and other citronella essential oil related [1]. Below we describe some of essential oil components and how its repellent activity towards insects [3].
Name of Oil | Composition | Insect Repellent Activity |
Citronella oil offers complete protection against common insects; however, this only lasts for up to two hours because of its fast evaporation property. Mixing citronella oil with larger molecules such as vanillin has been found to decrease volatility and improve protection over a longer duration. Comparison: citronella oil exhibits the same mosquito repellent effectiveness of DEET, for up to 2 hours. | ||
Lemongrass oil | Citral | 100% repellency for one hour at concentrations of 20% and 25% lemongrass oil in liquid paraffin. At both concentrations, protection efficiency decreased to 94% after three hours before decreasing to 44% after five hours of exposure. Results for concentrations of 10% and 15% were relatively similar over the measured time; however, full protection was lost within the first hour. Compared to the control sample, which contained pure citral, the samples containing essential oil performed substantially better. This would suggest that other components present in the oil decreased the volatility thus increasing protection effectiveness. |
Rosemary oil | 1,8-cineole Alpha-pinene Camphor Camphene | Rosemary oil has been proven to provide 100% protection for up to 8 h against Culex quinquefasciatus and Anopheles stephensi adult mosquitos. When compared to 11 other plant-based essential oils, rosemary essential oil proved to be the most effective by providing 100% repellence against Aedes aegypti for up to 90 min. |
Peppermint oil | Menthol Menthone | Chauhan et al. determined that peppermint oil exhibited 100% repellence against Musca domestica domestic house flies at a concentration of 0.010 μL/cm3. It performed slightly better but comparable to lemongrass essential oil with a repellent concentration RC95 = 0.009 μL/cm3. Compared to other essential oils, peppermint essential oil performed the worst against the larvae of Culex quinquefasciatus with an LC50 of 218.7 µL/L. |
Tea tree oil | Terpene-4-ol 1.8-cineole Gamma-terpinene Alpha-terpinene | Tea tree oil has proven to provide 78% protection for 30 min against Aedes aegypti, also known as the yellow fever mosquito. In a study by Edris et al., it was found that 1,8-cineole was the major constituent that was responsible for the insecticidal and repellent action against adult red floor beetles Tribolium castaneum and red imported fire ants Solenopsis invicta. |
Lemon tea tree oil | Citronella Citral | Lemon-scented tea tree from Leptospermum petersonii performed the best in the study by repelling the aforementioned species for 38 min, 60 min, 98 min, respectively. |
Lavender oil | Linalool | Lavender essential oil has proven to be 85.7% effective as a repellent against Culex quinquefasciatus for 8 h. Kulkarni et al. investigated the repellence and arvicidal effects of lavender essential oils from Lavandula gibsoni against adult Aedes aegypti and its larvae, the larvae of Anopheles sfttephensi, and Culex quinquefasciatus mosquitoes. At 2.0 mg/cm2, the essential oil of Lavandula gibsoni offered 100% protection for a period of 7h and 15 min against adult Aedes aegypti. |
Lemon eucalyptus oil | Citronellal | Due to the high volatility of citronellal, this repellent is only effective for up to 1 h. Kiplang’at and Mwangi found that at concentrations of 1%, lemon eucalyptus essential oil was more effective than neem oil at repelling Aedes aegypti mosquitos for 1 h with an effective repellence of 97.37% and 55.26%, respectively. |
Lemon eucalyptus oil derivative | para-menthane-3,8-diol | Isolated PMD oil has been found to be an effective repellent for up to 7.5 h. Laboratory studies confirmed that 30% PMD was as effective as 20% DEET against Anopheles mosquitoes. |
Sritabutra and Soonwera found that 10% clove oil mixed with olive oil offered full protection for about 76.5 min against Aedes aegypti mosquitoes. It was, however, much less effective against Culex quinquefasciatus mosquitoes, with an effective repellence of about 57 min compared to lemongrass and citronella grass oil, with effective repellences of about 97.5 min and 165 min, respectively. Clove essential oil and eugenol exhibited an LC50 = 57 and 93 ppm, respectively, while LC90 values were 86 and 158 ppm, respectively against Anopheles stephensi after exposure for 24 h. | ||
Cinnamaldehyde Eugenol | A study by Chaiphongpachara et al. proved that cinnamon essential oil was the most effective at eliminating Aedes aegypti larvae at LC50 = 0.03 ppm and LC90 = 0.04 ppm. It is known to also control the larvae of Culex tritaeniorhynchus successfully and Anopheles subpictus. Cinnamon essential oil proved as a very effective repellent against Aedes aegypti mosquitoes with a repellent dosage (RD50) of 75.92 mg. |
