Meliaceae
Azadirachta indica
Neem · Nimba · Indian lilac
- Part used
- leafseedoilbark
- Native range
- Indian subcontinent; widely planted and naturalised across the dry tropics, including northern Australia where it is a declared weed
- Morphology
- A fast-growing evergreen to twenty metres with pinnate leaves of curved toothed leaflets, sprays of small white honey-scented flowers, and olive-like fruit. Every part is intensely bitter.
What is in it
Evidence
Some trial evidence for neem-based dental preparations in plaque and gingivitis. Azadirachtin is a genuinely effective and widely used botanical insecticide, which is a finding about crops rather than people.
Safety
Neem oil is seriously toxic to infants and young children. Ingestion causes Reye-like syndrome — vomiting, drowsiness, seizures, metabolic acidosis, encephalopathy — and deaths are documented in the Indian paediatric literature, usually after oil given as a home remedy. Neem oil and seed extracts have documented antifertility effects in both sexes and are contraindicated in pregnancy.
Interactions: May lower blood glucose, compounding antidiabetic drugs; Immunomodulatory effects; caution with immunosuppressants
Regulatory: Permitted in topical and oral care products. A declared weed in the Northern Territory. Neem oil should never be given to infants.
How the traditions classify it
Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.
Historical use
Used across South Asia for at least two millennia for skin conditions, fever, dental care — neem twigs as toothbrushes are still ordinary — and as an agricultural insecticide and grain protectant.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
Worth knowing
Neem is at the centre of the best-known biopiracy case in modern intellectual property law.
In 1994 the European Patent Office granted a patent on a neem-based antifungal to the US Department of Agriculture and W.R. Grace. India objected that the use was ancient, documented and in the public domain, and after a decade of litigation the patent was revoked in 2005 — the opposition succeeding on the strength of prior use rather than prior publication.
The case, alongside comparable disputes over turmeric and basmati, is why India built the Traditional Knowledge Digital Library: several hundred thousand formulations transcribed and translated, held specifically so patent examiners can find them as prior art. It is one of the few concrete institutional answers anyone has built to the problem.
The paediatric toxicity deserves equal prominence. Neem oil is a household remedy across South Asia, and it kills infants.
Nomenclature verified against GBIF backbone taxonomy.