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.