Botanical Briefs: Neem Oil (Azadirachta indica)
Azadirachta indica, commonly known as neem, has many uses as a natural remedy. We review and discuss the pharmacologic, biologic, and medicinal properties of neem in disease management. We also report a rare clinical case of a 77-year-old man who presented with a hypopigmented rash on the lower back, bilateral flanks, and buttocks after 6 months of repeated application of neem oil to treat persistent arthritis and lower back pain.
Practice Points
- Neem is a traditional herb with various bioactivities, such as melanogenesis-inhibitory activity, toxicity against pests, antimalarial activity, and antioxidant activity.
- Neem should be used with caution as a remedy because of its skin-lightening properties, which are attributed to melanogenesis-inhibitory activity via tyrosinase inhibition.
- Chemical leukoderma should be included in the differential diagnosis when a patient presents with a hypopigmented rash after topical use of neem products.
Antimalarial Activity—One study indicated that nimbolide, a limonoid from the neem plant, demonstrated antimalarial activity against Plasmodium falciparum. In separate cultures of asexual parasites and mature gametocytes, parasite numbers were less than 50% of the number in control cultures (8.0% vs 8.5% parasitemia, respectively).14 Thus, the lower parasite numbers indicated by this study highlight the antimalarial utility of nimbolide and neem oil.
Antioxidant and Anti-inflammatory Activity—Neem bark has been reported to have considerable antioxidant activity due to its high phenolic content.1,15 One study showed that azadirachtin and nimbolide in neem exhibited concentration-dependent antiradical scavenging activity and antioxidant properties.16
The anti-inflammatory potential for neem may occur via the inhibition of the nuclear factor-κB signaling pathway, which is linked to cancer, inflammation, and apoptosis.17 It also has been observed that nimbidin within neem extracts—such as leaves, bark, and seed extract—suppresses the function of macrophages and neutrophils relevant to inflammation.16 Another study indicated neem’s anti-inflammatory activity due to the regulation of proinflammatory enzymes such as cyclooxygenase and lipoxygenase.18
Safety, Toxicity, and Risks
Ingestion—Although neem is safe to use in the general population, neem oil poisoning has been reported, particularly in young children. Ingesting large quantities of neem has resulted in vomiting, hepatic toxicity, metabolic acidosis, late neurologic sequelae, and encephalopathy in young children.19 The diagnosis of neem oil poisoning is based on patient history, clinical examination, and imaging findings. Poisoning can manifest as drowsiness, tachypnea, and generalized seizures.20
Topical Application—Topical use of neem appears to be safe if the substance is diluted with other ingredients. However, direct application to the skin is not advised, as it may cause leukoderma and could induce allergic contact dermatitis and other allergic reactions.4
Final Thoughts
The use of neem extract for disease prevention and treatment has been prevalent around the world since ancient times. Neem has been documented to possess melanogenesis-inhibitory activity, toxicity against pests, antimalarial activity, and antioxidant activity by means of tyrosinase inhibition, phytochemical production, limonoid expression, and nuclear factor-κB regulation, respectively. However, topical use of neem may trigger a cutaneous response, highlighting the importance of considering a diagnosis of neem oil–induced chemical leukoderma when patients present with a hypopigmented rash and relevant history.
