We use insect repellents to get rid of mosquitoes, cockroaches and so on. The widely used ingredient in those repellents is DEET (N, N-Diethyl-meta-Toluamide). It was proven to be very efficient in repelling insects.
DEET being a synthetic chemical however, has some shortcomings. First and foremost, it is toxic. It may cause encephalopathy in children. Besides, it was found that it may cause urticaria syndrome, anaphylaxis, hypertension and decreased heart beat. It also contributes to the environmental pollution. In short, it is harmful to human being and detrimental to the environment.
Due to the above disadvantages, people have been searching for natural repellents which do not have any side effects. Essential oils in plants were found to be a useful natural material as an alternative to the synthetic one.
There are a few essential oils found in plants that are concocted into the insect repellents.
Lemongrass (Cymbopogon citritus) is a tropical plant which root is used in cuisine. It contains citronellol which is a material that can be used to repel mosquitoes. It can give 2 hours of repellent effect after it is sprayed. This type of mosquitoes repellent could be found on sales in most supermarkets.
Neem oil from neem tree (Indian lilac, Azadirachta Indica) is also used as an ingredient. Neem oil is very useful as it could be used to prevent and repel 200 kinds of insects. It is very unique that it is not harmful to friendly insects like dragonfly, spider, earth worm, frog etc. It is of course, not harmful to human being. In fact, neem tree is the most useful plant as a source of essential oil for producing insect repellents.
The repellent properties of the essential oils are associated with the presence of mono terpenoids and sesquiterpenes. Examples of terpenoids are alpha-pinene, limonene, citronellol, citronellal, camphor, thymol etc.
Curry leaf was discovered to be a potential source of natural of essential ingredient oil for insect repellent concoction. It however, is more famous for use in culinary dishes as it gives special aroma and fragrance to the foods.
The scientific research found that the essential oil in curry leaf contains alpha-pinene and beta-myrcene. These two active ingredients have great potential to make curry leaf a source of essential oil for insect repellents.
Further effort need to be put in to carry out more researches and to commercialize the essential oil in curry leaf as an insect repellent.