Purported Benefits, Side Effects & More


Purported Benefits, Side Effects & More

Common Names

  • Margosa oil
  • Neem oil

For Patients & Caregivers

Tell your healthcare providers about any dietary supplements you’re taking, such as herbs, vitamins, minerals, and natural or home remedies. This will help them manage your care and keep you safe.

What is it?

Neem has been used in traditional and Ayurvedic medicine, but studies on safety and effectiveness are lacking.

Neem is an herb that is used as food, in traditional medicine for skin conditions, and for stomach ailments. It is also used as a disinfectant against pests and parasites. Some lab studies show that neem extracts have anticancer activities by inhibiting cancer cell growth. However, there are no human studies showing it to be an effective cancer treatment.

Although rare, serious adverse reactions caused by swallowing neem oil have been reported in both children and adults.

What are the potential uses and benefits?
  • Ulcers

    A small study found neem bark extract effective in reducing stomach acid secretion without any adverse effects. More studies are needed in humans.
  • Cancer

    In vitro studies suggest that neem can inhibit cancer cell growth. It has not been studied as a treatment for cancer.
  • Antiviral

    Neem extract increased CD4+ cell count and bodyweight in a small number of HIV+ volunteers. More studies are needed.
  • Oral hygiene

    Neem can reduce oral plaque and bacterial count. It is used as mouth rinse in traditional medicine.
What are the side effects?

Oral (Rare case reports): Vomiting, drowsiness, diarrhea, vision loss, toxicity to the nervous system, poisoning, seizures, and brain damage from swallowing neem oil.

Topical: Rash; itchy, dry or reddened skin

What else do I need to know?

Patient Warnings:

Swallowing neem oil has caused severe poisoning in both children and adults.

For Healthcare Professionals

Scientific Name
Azadirachta indica
Clinical Summary

Azadirachta indica or neem is a tree prevalent in South Asia. The bark, leaves, flowers, and seeds have been utilized as food and medicine for centuries. In Ayurvedic medicine, neem is used externally for skin conditions, internally for gastrointestinal ailments, and for oral hygiene. Several forms of neem extracts are marketed as dietary supplements.

Neem has antimicrobial activity and is used against a wide range of pests and parasites (1). It is effective against lice (2) and has antiretroviral activity (5). Neem also reduces plaque and decreases oral bacterial counts (3), but data are conflicting (4) (21). Its extracts were found to have anti-secretory and anti-ulcer properties (6), and to improve glycemic control in patients with metabolic syndrome (22).  Neem may also be effective in the treatment of cholera and diarrhea (7).

A few studies have examined the anticancer potential of neem. An ethanolic extract of neem leaves reduced the incidence of chemical-induced gastric tumors in mice  (9), and neem-treated monocytes induced apoptosis in cervical (10) and prostate cancer cells (11). Neem also showed chemopreventive effects in animal models (12). However, human data are lacking.

Although rare, case reports of poisoning and other severe adverse effects have been associated with the ingestion of neem oil.

Purported Uses and Benefits
  • Ulcers
  • Cancer
  • Infection
  • Oral hygiene
Mechanism of Action

The ulcer-healing properties of nimbidin from neem seeds are attributed to the stearic and palmitic acid components (14). Anti-ulcer effects are believed to be via inhibition of the proton pump, H+- K+- ATPase, to control secretion of hydrochloric acid and gastric mucus depletion, and prevent oxidative mucosal damage (6).

Azadirachta in neem has pestical activity due to its growth-regulating properties, reducing levels of the insect hormone ecdysone (14).

Neem induces cell death in prostate cancer cells by decreasing the levels of Bcl-2, an anti-apoptotic protein. Neem-treated monocytes induce apoptosis in cervical cancer cells by increasing levels of caspases 3, 8 and 9, interferon (IFN-gamma), and by decreasing tumor necrosis factor (TNF-alpha) (10). Neem also acts as an antiretroviral agent via inhibition of viral invasion of host cells (5).


Oral administration of neem oil resulted in severe poisoning in both children and adults. Vomiting, drowsiness, diarrhea, and vision loss have also been reported. In most serious cases, seizures associated with coma and even death have occurred (8) (18) (19) (20).

Adverse Reactions


  • Vomiting, drowsiness, diarrhea, vision loss, tachypnea with acidotic respiration, polymorphonuclear leukocytosis, encephalopathy, and seizures associated with coma (8) (18) (19) (20).
  • Poisoning and neurotoxicity requiring intensive medical care with mechanical ventilation (17).


  • Allergic contact dermatitis (15) (23).
  • Acute contact dermatitis: On the scalp and face of a patient following use of neem oil for alopecia (16).
  • Drug-Aggravated Bullous Pemphigoid: In a 47-year-old woman following use of neem oil for managing blisters on lower limbs, necessitating conventional treatment (24).
Herb-Drug Interactions

Cytochrome P450 substrates: A neem extract was shown to inhibit CYP 3A4/5, 2C8 and 2C9 enzymes in vitro. Clinical relevance is not known (25).

Dosage (OneMSK Only)
  1. Schmahl G, Al-Rasheid KA, Abdel-Ghaffar F, Klimpel S, Mehlhorn H. The efficacy of neem seed extracts (Tre-san, MiteStop on a broad spectrum of pests and parasites. Parasitol Res. Jul 2010;107(2):261-269.
  2. Abdel-Ghaffar F, Semmler M. Efficacy of neem seed extract shampoo on head lice of naturally infected humans in Egypt. Parasitol Res. Jan 2007;100(2):329-332.
  3. Pai MR, Acharya LD, Udupa N. Evaluation of antiplaque activity of Azadirachta indica leaf extract gel—a 6-week clinical study. J Ethnopharmacol. Jan 2004;90(1):99-103.
  4. Sharma S, Saimbi CS, Koirala B, Shukla R. Effect of various mouthwashes on the levels of interleukin-2 and interferon-gamma in chronic gingivitis. J Clin Pediatr Dent. Winter 2008;32(2):111-114.
  5. Udeinya IJ, Mbah AU, Chijioke CP, Shu EN. An antimalarial extract from neem leaves is antiretroviral. Trans R Soc Trop Med Hyg. Jul 2004;98(7):435-437. 6.
  6. Bandyopadhyay U, Biswas K, Sengupta A, et al. Clinical studies on the effect of Neem (Azadirachta indica) bark extract on gastric secretion and gastroduodenal ulcer. Life Sci. Oct 29 2004;75(24):2867-2878.
  7. Thakurta P, Bhowmik P, Mukherjee S, et al. Antibacterial, antisecretory and antihemorrhagic activity of Azadirachta indica used to treat cholera and diarrhea in India. J Ethnopharmacol. May 22 2007;111(3):607-612.
  8. National Institute of Diabetes and Digestive and Kidney Diseases. Margosa Oil. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. 2012-2014 Jan 30.
  9. Gangar SC, Koul A. Azadirachta indica modulates carcinogen biotransformation and reduced glutathione at peri-initiation phase of benzo(a)pyrene induced murine forestomach tumorigenesis. Phytotherapy Res. Sep 2008;22(9):1229-1238.
  10. Vasenwala SM, Seth R, Haider N, et al. A study on antioxidant and apoptotic effect of Azadirachta Indica (neem) in cases of cervical cancer. Arch Gynecol Obstet. 2012 Nov;286(5):1255-9.
  11. Kumar S, Suresh PK, Vijayababu MR, Arunkumar A, Arunakaran J. Anticancer effects of ethanolic neem leaf extract on prostate cancer cell line (PC-3). J Ethnopharmacol. Apr 21 2006;105(1-2):246-250.
  12. Dasgupta T, Banerjee S, Yadava PK, Rao AR. Chemopreventive potential of Azadirachta indica (Neem) leaf extract in murine carcinogenesis model systems. J Ethnopharmacol. May 2004;92(1):23-36.
  13. Mbah AU, Udeinya IJ, Shu EN, et al. Fractionated neem leaf extract is safe and increases CD4+ cell levels in HIV/AIDS patients. AmJ Ther. Jul-Aug 2007;14(4):369-374.
  14. Brahmachari G. Neem—an omnipotent plant: a retrospection. Chembiochem. 2004 Apr 2;5(4):408-21.
  15. Greenblatt DT, Banerjee P, White JM. Allergic contact dermatitis caused by neem oil. Contact Dermatitis. 2012 Oct;67(4):242-3.
  16. Reutemann P, Ehrlich A. Neem oil: an herbal therapy for alopecia causes dermatitis. Dermatitis. 2008 May-Jun;19(3):E12-5.
  17. Iyyadurai R, Surekha V, Sathyendra S, Paul Wilson B, Gopinath KG. Azadirachtin poisoning: a case report. Clin Toxicol (Phila). 2010 Oct;48(8):857-8.
  18. Bhaskar MV, Pramod SJ, Jeevika MU, et al. MR imaging findings of neem oil poisoning. AJNR Am J Neuroradiol. Aug 2010;31(7):E60-61.
  19. Mishra A, Dave N. Neem oil poisoning: Case report of an adult with toxic encephalopathy. Indian J Crit Care Med. Sep 2013;17(5):321-322.
  20. Suresha AR, Rajesh P, Anil Raj KS, et al. A rare case of toxic optic neuropathy secondary to consumption of neem oil. Indian J Ophthalmol. Mar 2014;62(3):337-339.
  21. Furquim Dos Santos Cardoso V, Amaral Roppa RH, Antunes C, et al. Efficacy of medicinal plant extracts as dental and periodontal antibiofilm agents: A systematic review of randomized clinical trials. J Ethnopharmacol. 2021 Dec 5;281:114541.
  22. Pingali U, Vuppalanchi B, Nutalapati C, Gundagani S. Aqueous Azadirachta indica (Neem) Extract Attenuates Insulin Resistance to Improve Glycemic Control and Endothelial Function in Subjects with Metabolic Syndrome. J Med Food. 2021 Nov;24(11):1135-1144.
  23. Bernaola M, Valls A, de Frutos C, Garcia-Abujeta JL. Occupational allergic contact dermatitis to neem oil used in natural cosmetic. Contact Dermatitis. 2020 Jun;82(6):389-390.
  24. N D, H H, N S, Chander J SJU. Drug-Aggravated Bullous Pemphigoid in a 47-year-old Asian Woman - A Case Report. Curr Drug Saf. 2022 May 18. doi: 10.2174/1574886317666220518091554. Online ahead of print.
  25. Amaeze O, Eng H, Horlbogen L, Varma MVS, Slitt A. Cytochrome P450 Enzyme Inhibition and Herb-Drug Interaction Potential of Medicinal Plant Extracts Used for Management of Diabetes in Nigeria. Eur J Drug Metab Pharmacokinet. 2021 May;46(3):437-450.
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