Neem

Azadirachta indica

Family: Meliaceae Part used: Leaves, seeds (oil), bark, flowers

Key Compounds

• Azadirachtin
• Nimbin
• Nimbidin
• Nimbolide
• Gedunin
• Salannin
• Quercetin
• Kaempferol
• Beta-sitosterol
• Catechin
• Gallic acid
• Oleic acid
• Linoleic acid

Traditional Use

• Organic pesticide — azadirachtin is a limonoid tetranortriterpenoid that disrupts insect development by blocking ecdysone (insect moulting hormone) receptors; larvae cannot complete metamorphosis; the mechanism is species-specific to insects and does not affect vertebrates, birds, or beneficial soil organisms at normal application concentrations; neem seed oil products standardised to azadirachtin are certified for organic agriculture and available globally; this is the largest commercial use of the neem tree worldwide
• Oral hygiene — chewing neem twigs (datun) is documented in Ayurvedic texts and continues as a daily practice across South Asia and Sub-Saharan Africa; the WHO has formally recognised neem twig chewing as effective for oral hygiene; the antimicrobial compounds (nimbidin, gallic acid, tannins) inhibit *Streptococcus mutans* and other oral pathogens; the twig's mechanical action combined with antimicrobial compounds provides both brushing and antibacterial effects
• Skin conditions — neem oil and leaf preparations used in Ayurvedic medicine for acne, eczema, psoriasis, and fungal skin infections; nimbidin inhibits prostaglandin synthesis (anti-inflammatory mechanism); the fatty acid profile of neem seed oil (oleic, linoleic acids) supports skin barrier function; topical application is the primary modern use in Western markets
• Antimalarial — gedunin and other limonoids show in vitro antiplasmodial activity against *Plasmodium falciparum*; used in traditional medicine in endemic malaria regions; clinical evidence is limited; not a replacement for pharmaceutical antimalarial treatment but documented in traditional use in Sub-Saharan Africa and South Asia
• Biopiracy controversy — in 1992 and 1994, W.R. Grace & Co. and the USDA filed patents for neem-based fungicides; in 1999 and 2005, after campaigns by the Indian government and European Green Party NGOs (particularly Vandana Shiva and the Research Foundation for Science, Technology and Ecology), the patents were successfully overturned at the European Patent Office; the ruling established that neem's medicinal and pesticidal properties had been documented in Indian traditional knowledge for millennia and could not be newly patented; this was among the first major biopiracy patent reversals

Neem is used as a pesticide in organic farming. This is the tree’s largest commercial application.

The leaves and seeds contain azadirachtin — a compound that blocks the hormone insects need to moult and complete metamorphosis. Larvae that encounter it cannot develop into adults. The mechanism is specific to insects. Vertebrates do not use ecdysone, which is why azadirachtin is certified for organic agriculture while being lethal to aphids and caterpillars. The same tree that Ayurvedic medicine calls sarvadosha nivarini — curer of all ailments — is also what organic farmers spray on crops.

Both things are true. They are not in conflict.

Meet the plant

A fast-growing tree of the Indian subcontinent and Burma, now cultivated throughout tropical and subtropical regions. It grows to 15–20 metres, produces white fragrant flowers, and bears small olive-like fruits containing a single seed — the seed with the highest azadirachtin concentration of any part of the plant.

Every part has a documented use: leaves, bark, seeds, flowers, root. This comprehensiveness is what the Sanskrit name sarvadosha nivarini was describing.

The pesticide mechanism

Azadirachtin is a limonoid tetranortriterpenoid — concentrated in the seed kernel, up to 0.3% by weight. It is an ecdysone antagonist: it occupies the binding site of the insect moulting hormone without triggering the moulting response. The larva cannot shed its skin and complete its development. It does not die immediately; it simply fails to progress through its life stages.

This mechanism is species-specific. Insects use ecdysone; vertebrates, birds, and most soil organisms do not. Agricultural application kills aphids, caterpillars, and other insect pests without the broad ecological damage of synthetic neurotoxic pesticides. This is why neem-based products carrying azadirachtin specifications are certified for organic agriculture in most countries.

The organic farming application is not a recent discovery. The insect-repelling and growth-disrupting properties of neem were known in South Asian agriculture for centuries — neem leaves were stored with grain, neem oil applied to crops, neem cake (the seed residue after oil pressing) worked into soil. Traditional agriculture used the same mechanism now encoded in modern organic certification.

The patent dispute

In 1992 and 1994, W.R. Grace & Co. and the USDA filed patents at the European Patent Office for neem-derived fungicidal and pesticidal formulations.

The Indian government, joined by environmental organisations including Dr. Vandana Shiva’s Research Foundation for Science, Technology and Ecology, challenged the patents. The argument: neem’s pesticidal and fungicidal properties had been documented in Indian traditional agricultural and medical practice for millennia. Patenting known traditional knowledge — granting a private corporation control over something communities had developed and freely shared — was biopiracy.

The EPO revoked the Grace/USDA patents in 1999 and 2005. The rulings became significant precedents in international debates about traditional knowledge and patent law. The patents were gone; the neem tree continued to grow where it had always grown.

The oral hygiene practice

Chewing a neem twig for oral hygiene — fraying the end until it becomes fibrous, using those fibres as a brush — is documented in Ayurvedic texts going back at least 2,000 years. It is practiced daily by millions of people across South Asia and Sub-Saharan Africa.

The WHO has formally recognised neem twig chewing as effective for oral hygiene. Clinical studies comparing neem chew sticks to conventional toothbrushes show comparable plaque reduction. The mechanism: mechanical action of the fibres plus antimicrobial compounds — nimbidin, catechins, gallic acid, tannins — that inhibit Streptococcus mutans and other oral pathogens.

No manufactured product required. The practice needs only the tree.

What people actually do with it

Topical (skin): Neem oil (from cold-pressed seeds) diluted 1:10 in carrier oil applied to acne, eczema, or fungal skin conditions twice daily. Pure neem oil has a strong, sulphurous smell and may irritate sensitive skin undiluted.

Oral hygiene (traditional): Fresh neem twig, 15–20 cm, chew the end until fibrous and use as a toothbrush. Allow twig to remain fresh (not dried). Most effective for people with access to growing trees.

Neem leaf tea (internal): 1 teaspoon dried neem leaf powder in hot water, steep 10 minutes. Bitter and unpalatable at full strength; dilute or blend with other herbs. Short-term use only.

Capsules: 500–1000 mg neem leaf extract daily, standardised preparations. Follow product instructions. Short courses; not for continuous long-term use.

Organic garden spray: Neem oil mixed with water and emulsifier (liquid soap), sprayed on affected plants. Standard organic pest management.

Caution: Neem seed oil is not for internal use. Toxic in children. Internal preparations are from leaf or bark, not seed oil.

Could you grow this yourself?

In tropical or warm subtropical climates — yes, easily. Neem is a fast-growing, drought-tolerant tree that asks little of its soil. It does not survive frost. In temperate climates it can be grown as a container specimen moved indoors for winter, but will not reach a size that provides useful leaf or seed material.

Neem (ニーム) in Japan

Japanese traditional medicine has no relationship with neem — the tree is not native to Japan and does not appear in kampo. Modern presence in Japan is through the supplement market and the organic agriculture sector. ニーム leaf supplements are positioned for immune support, skin health, and oral hygiene. Neem-based organic pesticides certified for Japanese organic agriculture are available through agricultural supply channels.

The oral hygiene application — neem toothpaste and chew sticks — appears in the Japanese natural health market, primarily associated with Ayurvedic connections.

Things you’re probably wondering

What does ‘sarvadosha nivarini’ mean? Sanskrit: sarva (all) + dosha (faults, ailments, imbalances) + nivarini (remover, curer). The traditional name describes a tree employed across the full range of Ayurvedic applications. It is a description of traditional use breadth, not a clinical efficacy claim.

Is neem toxic? The leaf in moderate doses has a long history of safe use. The seed oil is not for internal use and is toxic in children. Prolonged high-dose internal use of any neem preparation has been associated with liver stress. Short-term leaf preparations for the purposes documented in traditional medicine have a reasonable safety record.

Is the gedunin malaria claim real? Gedunin shows antiplasmodial activity against Plasmodium falciparum in laboratory studies. It is used in traditional medicine in malaria-endemic regions. Clinical trial evidence is limited. It is not a substitute for pharmaceutical antimalarial treatment. The traditional use is documented; the clinical evidence is preliminary.

Botanical details

The full compound list

See Also

• Tulsi / Holy Basil — Ayurvedic rasayana herb with similarly broad traditional application; different active chemistry
• Calendula — topical anti-inflammatory for skin; complementary approach to neem for skin conditions
• Moringa — another multi-use tree of South Asian traditional medicine with nutritional applications

References

• National Research Council (1992). Neem: A Tree for Solving Global Problems. The National Academies Press.
• Biswas, K. et al. (2002). Biological activities and medicinal properties of neem (Azadirachta indica). Current Science, 82(11), 1336–1345.
• Mossini, S.A. & Kemmelmeier, C. (2005). A árvore nim (Azadirachta indica A. Juss): muitos usos, múltiplos problemas. Semina: Ciências Biológicas e da Saúde, 26(1), 59–76.
• van der Nat, J.M. et al. (1991). Ethnopharmacognostical survey of Azadirachta indica A. Juss. Journal of Ethnopharmacology, 35(1), 1–24.