The neem tree has been called "the village pharmacy" because its bark, leaves, sap, fruit, seeds, and twigs have so many diverse uses in the traditional medicine of India. This member of the mahogany family has been used medicinally for at least 4,000 years and is held in such esteem that Indian poets called it Sarva Roga Nivarini, meaning "the One That Can Cure All Ailments." Mohandas Gandhi encouraged scientific investigation of the neem tree as part of his program to revitalize Indian traditions, which eventually let to more than 2,000 research papers and intense commercial interest.
At least 50 patents have been filed on neem and neem-based products in the United States for control of insects in food and ornamental crops. However, the Indian government and many nongovernmental organizations have united to overthrow some patents of this type, which they regard as "folk-wisdom piracy." One fear is that if neem is patented, indigenous people who already use it will lose the right to continue to do so. Another point is the fundamental question: Who owns the genetic diversity of plants? The nations where the plants come from or the transnational corporations that pay for the research into those plants? Although this area of international law is rapidly evolving, a patent on the spice turmeric has already been overturned, and neem may follow soon.
At least 100 bioactive substances have been found in neem, including nimbidin, azadiracthins, and other triterpenoids and limonoids. Although the scientific evidence for all of neem's uses in healthcare remains preliminary, the intense interest in the plant will eventually lead to proper double-blind, placebo-controlled trials. (For information on why such studies are so important, see Why Does This Database Rely on Double-blind Studies?)
The uses of neem are remarkably diverse. In India, the sap is used for treating fevers, general debilitation, digestive disturbances, and skin diseases; the bark gum for respiratory diseases and other infections; the leaves for digestive problems, intestinal parasites, and viral infections; the fruit for debilitation, malaria, skin diseases, and intestinal parasites; and the seed and kernel oil for diabetes, fevers, fungal infections, bacterial infections, inflammatory diseases, fertility prevention, and as an insecticide.1,2 However, there is no reliable research evidence to support any of these uses.
As with many plant products, test tube studies indicate that, on direct contact, neem can kill or inhibit the growth of bacteria, fungi, and viruses.4-8 This does not mean, however, that neem acts as a systemic antibiotic if it is taken by mouth. Neem mouthwash or chewing gum might be helpful for preventing cavities because it can directly come in contact with cavity-causing bacteria,4,8 but this has not been proven.
Because of the numerous parts of the neem tree used, and the many different ways these can be prepared, the only advice we can give at this time is to follow the directions on the label of the neem product you purchase.
Based on its extensive traditional use, neem seems to be quite safe. However, formal safety testing has only involved neem oil, the insecticide product made from the plant. While neem has been found adequately safe for use as an insecticide, animal studies suggest that long-term oral use of neem oil might produce toxic effects.10,11
In addition, other animal studies suggest that whole neem extract (which includes more substances than neem oil) may damage chromosomes, at least when taken in high doses or for an extended period of time.3,12
For all these reasons, as well as the lack of comprehensive safety investigation of neem products other than neem oil, we recommend that young children, pregnant or nursing women, or individuals with severe liver or kidney disease avoid use of neem.
1. Stix G. Village pharmacy. The neem tree yields products from pesticides to soap. Sci Am. 1992;266:132.
3. Awasthy KS, Chaurasia OP, Sinha SP. Prolonged murine genotoxic effects of crude extracted from neem. Phytother Res. 1999;13:81-83.
4. Almas K. The antimicrobial effects of extracts of Azadirachta indica (Neem) and Salvadora persica (Arak) chewing sticks. Indian J Dent Res. 1999;10:23-26.
5. Badam L, Joshi SP, Bedekar SS. 'In vitro' antiviral activity of neem ( Azadirachta indica. A. Juss) leaf extract against group B coxsackieviruses. J Commun Dis. 1999;31:79-90.
6. Juglal S, Govinden R, Odhav B. Spice oils for the control of co-occurring mycotoxin-producing fungi. J Food Prot. 2002;65:683-687.
7. SaiRam M, Ilavazhagan G, Sharma SK, et al. Anti-microbial activity of a new vaginal contraceptive NIM-76 from neem oil ( Azadirachta indica). J Ethnopharmacol. 2000;71:377-382.
Vanka A, Tandon S, Rao SR, et al. The effect of indigenous Neem ( Adirachta indica) mouthwash on Streptococcus mutans and lactobacilli growth. Indian J Dent Res. 2001;12:133-144.
9. Khosla P, Bhanwra S, Singh J, et al. A study of hypoglycaemic effects of Azadirachta indica (Neem) in normal and alloxan diabetic rabbits. Indian J Physiol Pharmacol. 2000;44:69-74.
10. Rahman MF, Siddiqui MK, Jamil K. LDH profiles of male and female rats treated with Vepacide. Phytother Res. 2002;16:122-126.
11. Rahman MF, Siddiqui MK, Jamil K. Effects of Vepacide ( Azadirachta indica) on aspartate and alanine aminotransferase profiles in a subchronic study with rats. Hum Exp Toxicol. 2001;20:243-249.
12. Awasthy KS. Genotoxicity of a crude leaf extract of neem in male germ cells of mice. Cytobios. 2001;106 Suppl 2:151-164.
Last reviewed December 2015 by EBSCO CAM Review Board
Last Updated: 12/15/2015