For Patients & Caregivers

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Neem has anticancer effects. More studies are needed to test its effects in humans.

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.

Adverse reactions caused by neem oil have been reported in both children and adults.

Purported Uses
  • 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 show neem can inhibit cancer cell growth. It has not been studied as a treatment for cancer.
  • Antiviral
    Neem extract has been shown to increase CD4+ cell count and bodyweight in a small number of HIV+ volunteers.
  • Oral hygiene
    Neem can reduce oral plaque and bacterial count. It is used as mouth rinse in traditional medicine.
  • Pesticide/fungicide
    Neem oil has been used externally against pests and lice.
Patient Warnings

Swallowing neem oil can cause severe adverse effects in children.

Side Effects
  • Vomiting, drowsiness, diarrhea, and seizures associated with coma have been reported.
  • Allergic contact dermatitis.
  • Acute contact dermatitis were observed on the scalp and face of a patient following use of neem oil for loss of hair.
  • Poisoning and neurotoxicity reported in a 35-year-old woman following consumption of a neem-based pesticide, requiring intensive medical care with mechanical ventilation.
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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. Currently, many 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). A neem bark extract was found to exhibit anti-secretory and anti-ulcer properties (6). 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.

Purported Uses
  • Ulcers
  • Cancer treatment
  • Antiviral
  • Antifungal
  • Oral hygiene
  • Pesticide
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 the inhibition of the proton pump, H+- K+- ATPase, to control the secretion of hydrochloric acid, inhibition of gastric mucus depletion, and prevention of 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 children. Vomiting, drowsiness and diarrhea have also been reported. In most serious cases, seizures associated with coma have occurred (8).

Adverse Reactions
  • Vomiting, drowsiness, diarrhea, tachypnea with acidotic respiration, polymorphonuclear leukocytosis, encephalopathy, and seizures associated with coma following oral administration of neem (8).
  • Allergic contact dermatitis (15).
  • Acute contact dermatitis on the scalp and face of a patient following use of neem oil for alopecia (16).
  • Poisoning with features of neurotoxicity in a 35-year-old woman following consumption of a neem-based pesticide, requiring intensive medical care with mechanical ventilation (17).
Herb-Drug Interactions

Some studies show that neem extracts have antioxidant activities. Theoretically, antioxidants can decrease the efficacy of certain chemotherapy drugs that rely on the generation of free radicals for their cytotoxic effects.

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. Parasitology research. 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. Parasitology research. 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. Journal of ethnopharmacology. 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. The Journal of clinical pediatric dentistry. Winter 2008;32(2):111-114.

  5. Udeinya IJ, Mbah AU, Chijioke CP, Shu EN. An antimalarial extract from neem leaves is antiretroviral. Transactions of the Royal Society of Tropical Medicine and Hygiene. Jul 2004;98(7):435-437. 6.

  6. Krieger R. Human Health Effects. 2001. Accessed August 8, 2013.

  7. Vasenwala SM, Seth R, Haider N, et al. A study on antioxidant and apoptotic effect of Azadirachta Indica (neem) in cases of cervical cancer. Archives of gynecology and obstetrics. Jun 21 2012.

  8. Kumar S, Suresh PK, Vijayababu MR, Arunkumar A, Arunakaran J. Anticancer effects of ethanolic neem leaf extract on prostate cancer cell line (PC-3). Journal of ethnopharmacology. Apr 21 2006;105(1-2):246-250.

  9. Dasgupta T, Banerjee S, Yadava PK, Rao AR. Chemopreventive potential of Azadirachta indica (Neem) leaf extract in murine carcinogenesis model systems. Journal of ethnopharmacology. May 2004;92(1):23-36.

  10. Mbah AU, Udeinya IJ, Shu EN, et al. Fractionated neem leaf extract is safe and increases CD4+ cell levels in HIV/AIDS patients. American journal of therapeutics. Jul-Aug 2007;14(4):369-374.

  11. Brahmachari G. Neem—an omnipotent plant: a retrospection. Chembiochem. 2004 Apr 2;5(4):408-21.

  12. Greenblatt DT, Banerjee P, White JM. Allergic contact dermatitis caused by neem oil. Contact Dermatitis. 2012 Oct;67(4):242-3.

  13. Reutemann P, Ehrlich A. Neem oil: an herbal therapy for alopecia causes dermatitis. Dermatitis. 2008 May-Jun;19(3):E12-5.

  14. 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.

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