In 2000, SaiRam et al. compared the efficacy of a spermicidal fraction derived from neem oil, NIM-76, to whole neem oil for antimicrobial activity against selected bacteria, fungi, and the polio virus in mice. NIM-76 was found to inhibit the growth of Escherichia coli and Klebsiella pneumoniae, neither of which were affected by whole neem oil. In addition, NIM-76 displayed antifungal and antiviral activity, respectively, against Candida albicans and polio virus replication. Systemic candidiasis was prevented by NIM-76 as suggested by greater percentage survival and diminished C. albicans colonies in several tissues. The authors concluded that the neem oil derivative exhibits strong broad-spectrum antimicrobial properties (J. Ethnopharmacol. 2000;71:377-82).
Other Properties of Neem Under Study
In 2007, Abdel-Ghaffar and Semmler studied the results of a neem seed extract shampoo on 60 male and female children (between ages 4 and 15 years) who were chosen based on heavy lice infestation. Each patient had their completely wet hair thoroughly washed with 20-30 mL of the shampoo, with rubbing applied to ensure that the shampoo reached the scalp skin. The shampoo was rinsed out after 5, 10, 15, or 30 minutes, and head lice were then collected and examined. The neem seed extract shampoo was found to be extremely effective against all head lice stages, with no differences seen after shampoo exposures of 10, 15, or 30 minutes and no side effects observed (Parasitol Res. 2007;100:329-32). Notably, the commercially available water-free neem seed extract shampoo Wash-Away Louse was found to be efficacious against Sarcoptes scabiei in a recent small study of dogs in Egypt conducted by Abdel-Ghaffar et al. After 14 days of daily topical treatment with the shampoo, 8 of the 10 dogs were completely cured and just a small number of mites were detected in 2 dogs. No adverse reactions were observed as clinical signs thoroughly cleared (Parasitol Res. 2008;104:145-8).
In 2006, Heukelbach et al. evaluated Wash-Away Louse shampoo for its in vitro effects on head lice. Head lice (totaling 17) culled from two Australian school children and their mothers, separated by a month, were immersed in the shampoo. A dissecting microscope was used for over 2 hours to examine the vitality of the parasite. A commercially available head lice treatment with permethrin 1% was used on 19 lice as a positive control and no treatment (for 14 lice) served as the negative control. After 3 hours, only one louse of the original 17 showed minor signs of life in the neem shampoo group, a mortality rate of 94%. After 3 hours, the mortality rate in the permethrin group was 74%; none of the lice in the negative group died during the observation period. The investigators concluded that the neem shampoo is very effective in vitro against head lice and more effective than a 1% permethrin-based product (Parasitol. Res. 2006;99:353-6).
In 2004, Dasgupta et al. investigated the anticarcinogenic potential (specifically, on skin papillomagenesis) and compared the effects of two different doses of 80% ethanolic extracts of Azadirachta indica leaves on drug-metabolizing phase I and phase II enzymes, antioxidant enzymes, glutathione content, lactate dehydrogenase, and lipid peroxidation in the liver of 7-week-old Swiss albino mice. They observed a significant inhibition of tumor burden (as measured by decreases in the average number of papillomas per mouse and percentage of tumor-bearing mice) and a reduction of tumor incidence associated with both doses (250 and 500 mg/kg body weight) of neem leaf extract. In addition, the researchers found the potential of the extract to induce only the phase II enzymes linked to carcinogen detoxification in murine liver. Notably, both doses of neem were shown to be effective in raising the activity levels of various antioxidant enzymes, including hepatic glutathione reductase, glutathione peroxidase, superoxide dismutase, and catalase. The authors concluded that Azadirachta indica exhibits strong potential to suppress chemical carcinogenesis at the initiation stages (J. Ethnopharmacol. 2004;92:23-36).
It should be noted that the use of neem oil has been associated with systemic as well as contact reactions (Dermatitis 2008;19:E12-5). In a recent study of 14 products primarily intended for agricultural use that were assessed for acute dermal and ocular effects, the most significant reactions occurred around the eyes from the use of azadirachtin, an active principle of neem (Cutan. Ocul. Toxicol. 2008;27:173-85).
In addition to the shampoos and spermicides mentioned above, neem is found in various soaps as well as cosmetic waxes and lubricants.
Conclusion
The depth and breadth of traditional and modern medical applications of neem are compelling. Neem is useful and effective in some modern dermatologic treatments. More research is necessary to determine how best to harness the many parts of this medically active tree for additional uses in dermatology as well as other branches of medicine.