Neem by Herbal Hills

POSSIBLY EFFECTIVE

• Dental plaque. Topical neem mouth rinses and gel extracts may reduce dental plaque. It is unclear if neem is as effective as chlorhexidine for this purpose. Details: Clinical research shows that using neem topically as a mouth rinse or gel extract twice daily for 3 weeks to 3 months can reduce dental plaque in some patients (12824,64845,94567,97926,104182). Neem leaf extracts, including one at a concentration of 2.5%, have been applied to the teeth and gums twice daily for up to 3 months (12824,64845,104182). Rinsing with 5 mL of neem solution (concentration unknown) or 15 mL of neem 2% solution twice daily for up to 30 days has also been used (94567,97926). It is unclear how neem compares to chlorhexidine for this purpose. One small clinical trial shows that applying neem gel shows similar improvements in plaque index when compared with chlorhexidine 0.2% gel (104182), while another small study shows that rinsing with a neem solution may not be as effective as chlorhexidine 0.2% solution for reducing dental plaque (97926). Reasons for these disparate findings are unclear, but may be related to differences in patient populations, formulations used, and study length.
• Gingivitis. Topical neem mouth rinses and gel extracts may reduce gingivitis, but neem may not be effective in patients with chronic gingivitis. It is unclear if neem is as effective as chlorhexidine for this purpose. Details: Clinical research shows that using neem topically as a mouth rinse or gel extract twice daily for 3 weeks to 3 months appears to improve gingivitis in some patients (12824,64845,94567,104182). However, neem may not be effective in patients with chronic gingivitis (64850). Neem leaf extracts, including one at a concentration of 2.5%, have been applied to the teeth and gums twice daily for up to 3 months (12824,64845,104182). Rinsing with 15 mL of neem 2% solution twice daily for 3 weeks has also been used (94567). It is unclear how neem compares to chlorhexidine for this purpose. One small clinical trial shows that applying neem gel shows similar improvements in gingival index when compared with chlorhexidine 0.2% gel (104182), while other small studies show that rinsing with neem solution may not be as effective as chlorhexidine 0.2% solution for reducing gingivitis (97926,97927). Reasons for these disparate findings are unclear, but may be related to differences in patient populations, formulations used, and study length.
• Lice. Topical neem extract shampoo may treat lice in children. Details: Clinical research in children 2-11 years of age with head lice shows that applying a single application of neem extract shampoo (Licener Pronovo Laboratories) 100 mL to dry hair for 10 minutes followed by rinsing with warm water eradicates 100% of head lice. A single application of neem extract shampoo appears to be slightly more effective than dimethicone (silicone oil) shampoo (97928).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acne. Topical neem extract has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: An observational study in adults who have mild to moderate acne or those without current lesions who are prone to acne, shows that using a specific face wash containing unknown amounts of neem extract and turmeric extract (Himalaya's Purifying Neem Face Wash; Himalaya Drug Company) twice daily for 28 days reduces new inflammatory and non-inflammatory acne lesions by 45% and 69%, respectively, when compared with baseline (107883). The validity of these findings is limited by the lack of a comparator group and short duration of treatment; additionally, it is unclear if this effect is due to neem extract, other ingredients, or the combination.
• Abortion. Although there has been interest in using oral neem to induce abortion, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Asthma. Although there has been interest in using oral neem for asthma, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Cardiovascular disease (CVD). Although there has been interest in using oral neem for CVD, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Contraception. Although there has been interest in using oral and intravaginal neem for contraception, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Coronavirus disease 2019 (COVID-19). There is limited evidence on the oral use of a neem leaf extract in preventing COVID-19 in high-risk individuals. Details: A clinical study in adults at high risk for COVID-19 infection (e.g. healthcare workers and relatives of patients with COVID-19) shows that taking a specific capsule formulation of neem leaf extract (Nisarga's Neem; Nisarga Biotech) 50 mg twice daily for 28 days decreases the rate of COVID-19 infections by day 29 to 4%, compared with 10% of patients in the placebo group. This suggests that 17 patients would need to take this product to prevent one infection (107882). The validity of this study is limited by the short duration of treatment and unclear reporting. Additionally, patients were only tested for COVID-19 at baseline, day 29, or if symptoms were present; therefore, asymptomatic COVID-19 infections may have been underreported.
• Cough. Although there has been interest in using oral neem for cough, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Diabetes. It is unclear if oral neem extract is beneficial in patients with diabetes. Details: One small clinical trial in patients with type 2 diabetes who are taking metformin shows that taking a specific neem leaf and twig extract (PhytoBGS; Natreon Inc) 125 mg, 250 mg, or 500 mg twice daily for 12 weeks improves glycemic control in a dose-dependent manner. When compared with placebo, reductions in fasting plasma glucose with neem extract ranged from 8-22 mg/dL and reductions in glycated hemoglobin ranged from 0.18% to 1.47%. Postprandial glucose and measures of insulin resistance and endothelial function were also improved (104181).
• Dyspepsia. Although there has been interest in using oral neem for dyspepsia, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Hemorrhoids. Although there has been interest in using topical neem for hemorrhoids, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Insect repellent. Although there has been interest in using topical neem as an insect repellent, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Intestinal parasite infection. Although there has been interest in using oral neem for intestinal parasite infections, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Metabolic syndrome. It is unclear if oral neem leaf and twig extract is beneficial in patients with metabolic syndrome. Details: One clinical trial in patients with metabolic syndrome shows that taking a specific neem leaf and twig extract (PhytoBGS; Natreon Inc) 250 mg or 500 mg twice daily for 12 weeks improves glycemic control in a dose-dependent manner when compared with placebo. In the treatment group, reductions in fasting plasma glucose, postprandial plasma glucose, and glycated hemoglobin (HbA1c) ranged from 3-6 mg/dL, 0.7-5.4 mg/dL, and 0.6% to 1.7%, respectively (107881). However, there was no improvement in lipid parameters, and a lower dose of 125 mg twice daily did not affect any measurements (107881). The validity of this study is limited due to unclear reporting.
• Mosquito repellent. Small clinical studies suggest that topical creams containing neem oil may provide moderate to high-level protection against mosquitos. Details: Several small clinical studies show that topical application of a cream containing neem oil 1%, 2%, or 5% provides 37.5% to 100% protection against mosquitoes when compared with a placebo cream. Effectiveness seems to vary depending on mosquito species and geographic location (64876,64878,64882).
• Osteoarthritis. Although there has been interest in using topical neem for osteoarthritis, there is insufficient reliable information available about the clinical effects of neem for this condition.
• Peptic ulcers. It is unclear if oral neem is beneficial in patients with peptic ulcers. Details: One small, uncontrolled clinical study in six patients with peptic ulcers shows that taking neem bark extract 30-60 mg twice daily for 10 weeks reduces gastric secretions when compared to baseline and might aid in the healing of gastroduodenal ulcers. All patients treated with neem bark extract experienced at least 80% healing of gastroduodenal ulcers (12822). The validity of these findings is limited by the very small study size and the lack of a control group.
• Psoriasis. It is unclear if oral neem is beneficial in patients with psoriasis. Details: One small clinical trial in patients with uncomplicated psoriasis shows that taking neem extract by mouth daily in combination with daily sun exposure and application of a Vaseline-based cream containing crude coal tar and salicylic acid for 12 weeks reduces psoriasis symptom severity by approximately 50% when compared with placebo (64892).
• Scleroderma. Topical neem has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Observational research in patients with systemic sclerosis has found that topical application of a specific cream (Holoil, RI.MOS. SRL) containing neem oil and St. John's wort extract seems to improve the healing of skin ulcers, decrease pain, reduce the need for surgical removal of lesions, and reduce the risk of infections and need for antibiotic therapy when compared with a control group (102867). It is unknown if these effects are due to neem, St. John's wort, or the combination. Additionally, the validity of these results is limited by a lack of randomization, blinding, and placebo-control.
• Tungiasis. It is unclear if topical neem oil is beneficial for the treatment of tungiasis. Details: One small clinical trial in children aged 6-15 years with tungiasis shows that topical application of an oil mixture containing neem seed oil 20% and virgin coconut oil 80%, 1 drop on days 1 and 3, kills about 40% of sand fleas within 7 days, a rate similar to standard treatment with a potassium permanganate 0.05% foot bath (104258).
• Urinary tract infections (UTIs). Although there has been interest in using oral neem for UTIs, there is insufficient reliable information available about the clinical effects of neem for this purpose.
• Wound healing. Topical neem has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-size clinical study in adults with dehisced post-surgical wounds shows that applying a specific aerosol product (1PWD, Kerecis AG) containing neem oil and St. John's wort to wounds during dressing changes does not improve wound healing scores at day 28 but may reduce pain scores when compared with silver-based dressings (alginates or polyurethane foam) (111592). However, this study may have been inadequately powered to detect a difference between groups. It is also unclear if these affects are due to neem, St. John's wort, or the combination. More evidence is needed to rate neem for these uses.

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POSSIBLY SAFE ...when neem bark extract is used orally and appropriately, short-term. Neem bark extract has been used safely in clinical research at doses up to 60 mg daily for up to 10 weeks (12822). ...when neem leaf and twig extract is used orally and appropriately, short-term. Neem leaf and twig extract has been used safely in clinical research at doses up to 500 mg twice daily for up to 12 weeks (104181). ...when neem leaf extract gel is used intraorally for up to 6 weeks (12824,64845,64850,94567). ...when neem oil, cream, or face wash is used topically on the skin for up to 2 weeks (64876,64878,64882,102867,107883).

POSSIBLY UNSAFE ...when neem or neem oil is used orally in large amounts or long-term. Preliminary clinical research suggests neem might be toxic to the kidneys or liver with high-dose or chronic use. Cardiac arrest has also been reported (12835,64870,64873).

CHILDREN: POSSIBLY SAFE
when neem extract is used topically. It has been used with apparent safety as a shampoo, with one or two total applications (97928).

CHILDREN: LIKELY UNSAFE
when neem oil or seeds are used orally. There are reports of infants who were severely poisoned and died after oral use of neem (3473,3474,3476,64855,64875).

PREGNANCY: LIKELY UNSAFE
when neem oil or leaf is used orally. Neem oil and leaf have been used as abortifacients (12825,12835,64884,64889).

LACTATION:
Insufficient reliable information available; avoid using.

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ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Neem might increase the risk of hypoglycemia when taken with antidiabetes drugs.  Details Some clinical research shows that neem can lower blood glucose levels in adults with type 2 diabetes, including those already taking metformin (12823,104181).

CYTOCHROME P450 2C8 (CYP2C8) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, neem leaf extract might increase the levels and clinical effects of CYP2C8 substrates.  Details In vitro research shows that neem leaf methanol extract inhibits CYP2C8 enzymes (111593). So far, this reaction has not been reported in humans.

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, neem leaf extract might increase the levels and clinical effects of CYP2C9 substrates.  Details In vitro research shows that neem leaf methanol extract inhibits CYP2C9 enzymes (111593). So far, this reaction has not been reported in humans.

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, neem leaf extract might increase the levels and clinical effects of CYP3A4 substrates.  Details In vitro research shows that neem leaf methanol extract inhibits CYP3A4 enzymes (111593). So far, this reaction has not been reported in humans.

IMMUNOSUPPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, neem might decrease the effectiveness of immunosuppressants.  Details Animal research suggests that neem might have immunostimulant effects (12825).

P-GLYCOPROTEIN SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, neem leaf extract might increase the levels and clinical effects of P-glycoprotein substrates.  Details In vitro research shows that neem leaf methanol extract inhibits renal P-glycoprotein transport activity (107850). So far, this reaction has not been reported in humans.

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General ...Orally, neem extracts seem to be well tolerated in adults. However, high-quality assessment of safety has not been conducted. In children, oral use of neem oil can cause serious adverse effects. Topically, neem seems to be well tolerated in children and adults.
Most Common Adverse Effects:
Topically: Contact dermatitis in sensitive individuals.
Serious Adverse Effects (Rare):
Orally: Cardiac arrest, nephrotoxicity, and ventricular fibrillation with neem leaf in adults. Encephalopathy, hematologic abnormalities, hepatotoxicity, and nephrotoxicity with neem oil in infants and young children.

Cardiovascular ...Orally, neem leaf has been reported to cause ventricular fibrillation and cardiac arrest after ingestion in humans (64873,64870).

Dental ...Topically, use of neem twigs to brush teeth, which is a traditional dental hygiene practice in India, has been associated with vitiligo of the lips. The limonoid constituents in neem, which have been shown to inhibit melanogenesis and have cytotoxic effects, combined with repeated, local trauma from this dental hygiene practice are thought to cause this leucodermic reaction. In a case series of seven patients experiencing vitiligo of the lips from neem twigs, use of toothpaste and topical tacrolimus along with avoidance of neem stopped the progression of depigmentation in all patients. Repigmentation was reported in four of the seven patients 12 months after discontinuing neem-based dental hygiene practices (100958).

Dermatologic ...Topically, neem products have been associated with dermatologic reactions. Some case reports have associated the use of topical neem oil with contact dermatitis (64851,94568,102867). In one case series, the topical application of neem seed extract shampoo was associated with skin irritation, red spots, and a burning feeling of the scalp (64848). Use of neem twigs to brush teeth, which is a traditional dental hygiene practice in India, has been associated with vitiligo of the lips. The limonoid constituents in neem, which have been shown to inhibit melanogenesis and have cytotoxic effects, combined with repeated, local trauma from this dental hygiene practice are thought to cause this leucodermic reaction. In a case series of seven patients experiencing vitiligo of the lips from neem twigs, use of toothpaste and topical tacrolimus along with avoidance of neem stopped the progression of depigmentation in all patients. Repigmentation was reported in four of the seven patients 12 months after discontinuing neem-based dental hygiene practices (100958).

Gastrointestinal ...Orally, neem oil has been reported to cause vomiting and loose stools in infants and small children (3473,3474,3476,64865).

Genitourinary ...Orally, neem leaf has been reported to cause oliguria and anuria in adults (12833,12834). After a single intrauterine instillation, purified neem oil has been reported to cause endometritis in healthy, tubectomised females (64886).

Hematologic ...Orally, neem leaf has been reported to cause hemolysis in adults (12835). In one case report, a 35-year-old male with diabetes and glucose-6-phosphate dehydrogenase (G6PD) deficiency developed hemolytic anemia and jaundice after drinking several liters of neem tea daily for 3 weeks. All symptoms resolved after discontinuation and supportive treatment (94571). Orally, neem oil has been reported to cause metabolic acidosis, anemia, and polymorphonuclear leukocytosis in infants and young children (3473,3474,3476,64865).
A single intrauterine instillation of purified neem oil has been reported to cause mild transient eosinophilia in healthy, tubectomised females (64886).

Hepatic ...Orally, neem oil has been associated with reports of hepatotoxicity in infants and children. These adverse effects occurred after single doses of neem oil ranging from a few drops to 60 mL. Pathologic findings on liver biopsy reports have been consistent with Reye-like syndrome (3473,3474,3475).

Immunologic ...Topically, a case of aggravated bullous pemphigoid requiring hospitalization is reported in a 47-year-old patient with this autoimmune condition after application of neem oil to blisters for an unknown duration (111715).

Neurologic/CNS ...Orally, single doses of neem oil ranging from a few drops to 60 mL have been associated with reports of encephalopathy in infants and small children. Symptoms include drowsiness, seizure, loss of consciousness, coma, cerebral edema, Reye-like syndrome, and death within hours of ingestion (3473,3474,3476,3476,64855,94750). There is also at least one case report of neurotoxicity in an adult after ingestion of a neem-based pesticide. A 35-year-old female experienced neurotoxicity requiring intensive medical care and ventilation after ingestion of a pesticide containing azadirachtin, a constituent of neem oil (64858).

Ocular/Otic ...In one case report, a 35-year-old female developed toxic optic neuropathy and vision loss in both eyes lasting for two days after consuming 150 mL of neem oil in a suicide attempt five days earlier (64856).

Renal ...Orally, neem leaf has been reported to cause oliguria, anuria, acute tubular necrosis, and nephrotoxicity in adults (12833,12834). There are some case reports of children developing Reye-like syndrome after ingestion of neem oil. Pathologic findings on renal biopsy reports have been consistent with Reye syndrome (3473,3474,3475).

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