Active Chemicals
Neem oil is made from the seeds of the neem tree, known scientifically as Azadirachta indica. According to James Duke, Ph.D., the active chemicals in neem seed oil are azadirachtin, nimbidin, salannin, azadiradione, azadirone, gedunin, meldenin and meliantriol (see link in References). Neem oil functions as a medicine, pesticide and fungicide. Medicines and personal care products made from pure neem oil may contain all the active chemicals in varying amounts. Pesticide products made from neem oil usually extract the azadirachtin and standardize it. Fungicide products also remove the azadirachtin, but use the remaining oil as the fungicide.
Medicine and Personal Care
Neem oil is used in Ayurvedic treatments and personal care items. The oil can be mixed into salves, liquid soap, toothpaste, skin creams, shampoos, lotions and powders. Neem oil is considered to be anti-inflammatory, antibacterial, antiviral, antiseptic, antimalarial and larvicidal. This activity may be due either to a single chemical in the oil or to the effects of synergism--the way all the plant's chemicals interact.
One of neem oil's constituents, nimbidin, possesses powerful anti-arthritic and anti-inflammatory activities, making it useful in treating inflammatory diseases, such as arthritis, acne, hives, eczema and psoriasis. Inflammation is one way the body heals itself, but if the inflammatory process continues indefinitely, chronic disease and possible organ failure may develop. Neem oil is useful in treating inflammatory diseases because nimbidin helps the body switch off the inflammatory response. In skin diseases, neem oil's antibacterial and antiviral actions also protect broken skin from further injury.
The chemicals in neem oil are important anti-malarials. They work by killing the larva of the Anopheles mosquito that transmits the malaria parasite. The oil can be sprayed on mosquito nets and is preferable to chemical pesticides because it is environmentally safe.
Insecticide and Fungicide
According to the U.S. Environmental Protection Agency, neem oil is a safe and effective pesticide that works by interrupting the life and growth cycles of crop-destroying insects while not harming beneficial insects, such as butterflies and pollinators.
Two standardized ingredients used in commercial neem oil pesticides are azadirachtin and clarified hydrophobic extract of neem oil. Azadirachtin is extracted from neem oil by treating it with alcohol. Its chemical properties mimic the hormones found in insect pests, such as grasshoppers, leaf hoppers, white flies, locusts, mites and aphids. Once ingested, these chemicals inhibit insects from eating, mating and growing. Eventually the insect dies, and since the reproductive cycle is interrupted, the benefits are long term.
Clarified hydrophobic extract of neem oil works like standardized azadirachtin, but it also has antifungal activity and can protect plants from mildews and rusts. Since insects treated with neem oil products do not die immediately, pest control with neem oil takes longer than with ordinary chemical pesticides. But neem oil is non-toxic, when used correctly, and biodegradable, making it safer for humans, animals and the environment.
Warnings
Neem oil should not be used by pregnant women because some of the chemicals in neem oil products can induce miscarriage. Neem oil has also been used as an abortifacient because its anti-estrogenic action can prevent embryo implantation.
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