Potential Benefits and Dangers of Neem Oil
For over 4,000 years, the neem tree has been used in traditional medicine. Abundant in bioactive compounds, neem is a natural antiseptic that can be used on the skin, hair, in cosmetics, on pets, and in your garden. The oil may even work as a cheap, natural contraceptive for reducing population overgrowth. If you’re as intrigued as we were, read on to learn more about this plant.
What Is Neem Oil?
The Swahili word for the tree, Mwarobaini, translates to “tree of 40,” as the tree is traditionally used to remedy 40 different diseases. In India, it’s sometimes referred to as ‘nature’s drug store’ due to its many traditional health uses [R+, R, R].
It’s been used in Ayurvedic medicine, a system of traditional medicine that originated in India, for over 4,000 years [R+].
Virtually every part of the tree, including the bark, seeds, leaves, flowers, and roots, have traditional medicine uses. For example, chewing neem twigs is a common method for keeping the teeth clean in some rural Indian populations [R, R, R].
Neem oil usually refers to the oil obtained from neem seeds, although extracts from other parts of the tree, like the leaves, are also sometimes called ‘neem oil.’ The oil has a yellow color and reportedly smells like garlic [R+, R+].
Snapshot of Neem Oil
- May improve skin and hair health
- Helps wounds heal faster
- Improves oral health
- May be used for skin problems in pets
- A natural pesticide
- Extracts may protect the kidneys, liver, heart, and brain
- Extracts might be useful for cancer and diabetes
- Can cause ‘neem oil poisoning’ and allergic reactions
- Research is limited and some studies are flawed
- Wide variety of formulations with different effects
Over 300 compounds have been identified in neem [R].
Neem oil also contains a group of compounds called limonoids, the most well-known of which is azadirachtin. The plant makes these compounds to deter predators, and they are likely responsible for many of its bacteria- and pest-killing properties [R+, R, R+].
How Does Neem Oil Work?
Neem oil can kill bacteria and fungi cells by destroying their cell wall. This bacteria-killing ability is likely how neem oil improves acne and dandruff. It’s also why neem can be effective in products like toothpaste [R, R, R+, R, R+].
Neem is commonly used in cosmetics. It may promote wound healing by activating the immune system and helping form new blood vessels. The antioxidants in neem likely protect the skin by scavenging free radicals that can damage cells and cause skin aging [R, R+, R+, R+].
Neem oil can also kill insects, ticks, and mites. It may work by damaging the organs these pests need to feed. This is how neem functions as a pesticide and also how it can be effective at resolving infestations of scabies [R, R, R, R, R].
When used orally, neem extracts may help prevent cancer. Compounds in neem oil may work by:
- Increasing the activity of enzymes that can remove cancer-causing chemicals, including those that help glutathione bind to toxins (glutathione S-transferases) [R+, R].
- Antioxidant activity, which can protect cell DNA from mutations that can lead to cancer [R+].
- Increasing the activity of DNA-repairing proteins, which also help prevent mutations [R].
In existing tumors, components of neem oil may prevent tumor growth by:
- Causing cancer cells to stop dividing [R, R+].
- Lowering tumor-promoting proteins the cancer cells produce [R+].
- Killing cancer cells by activating programmed cell death pathways [R+, R, R].
- Activating the immune system [R+, R].
- Restricting the blood supply of the tumor, essentially starving it [R+].
Health Benefits of Neem Oil
Pure neem oil can be applied directly to the skin or hair. It is also added to beauty products, often in combination with other oils, herbs, or active compounds. Additionally, pills with neem extracts may be more effective for some skin conditions than the oil. This section covers the health benefits of both the oil and the extracts.
1) Psoriasis, Acne, and Skin Health
Aside from herbal combinations, taking extracts only from neem may improve skin diseases. In a study of 50 people with psoriasis, an extract from its leaves in addition to standard treatment reduced symptoms after 3 months better than standard treatment alone [R+].
Neem oil is anecdotally lauded for its ability to keep the skin healthy and looking young, but there isn’t much solid science to back up these claims.
One study did find that an extract of neem leaves prevented UVB-induced wrinkling in mice. In this study, neem reduced free radicals, which blocked enzymes that break down collagen. As a result, it boosted production of both collagen and elastin–two key skin-protecting compounds needed to maintain youthful, healthy skin [R].
Additionally, neem may help skin wounds heal faster. In a study of nine people, oil from neem and St. John’s wort applied as a skin dressing safely enhanced the healing of scalp wounds following surgery when. However, this study lacked a control group [R].
2) Head Lice and Hair Health
One study including 60 children with lice reported that a treatment including a neem extract-containing shampoo was effective, but due to the lack of a control group, it’s impossible to say whether the plant extracts themselves were beneficial [R].
Although there are numerous claims that neem oil can help with dandruff, there haven’t been rigorous studies in humans to back these claims up. However, neem oil can prevent the growth of dandruff-causing bacteria and fungi in dishes [R, R, R+, R+, R+].
Similarly, whether neem oil can promote hair growth or prevent baldness in humans hasn’t been thoroughly tested, though there is an abundance of anecdotal evidence. Neem oil did speed up hair growth in rabbits [R+, R+, R+].
3) Cancer and Radiation Side Effects
In a small study of 28 people with head and neck cancer, a treatment including neem oil and St John’s wort reduced skin irritation from radiation therapy. However, this study didn’t have a control group, making it impossible to rule out placebo effect [R].
In mice and rats given cancer-causing chemicals, neem extracts prevented the development of tumors and pre-tumor lesions; the tumors that did develop were generally smaller than those in controls [R+, R, R, R].
4) Dental Health
Studies including over 130 healthy people found that neem-based mouthwashes improved oral health. Neem-based mouthwashes reduced plaque, decreased gum inflammation, and killed mouth bacteria just as much as, or more than, a standard mouthwash [R, R, R, R].
A study including 45 people with gingivitis (gum inflammation) found that a neem-based mouthwash reduced symptoms such as gum bleeding and the buildup of plaque just as well as a standard of care mouthwash [R].
Additionally, one study including 50 healthy people reported that chewing neem sticks was equally as effective at keeping the mouth clean as using a toothbrush. Stick chewers even had a greater reduction in plaque than tooth brushers [R].
5) Killing Bacteria and Fungi
Directly tied to many of its benefits–including those for skin, hair, and oral health–neem oil is a potent antiseptic. In numerous studies, the oil could kill or prevent the growth of disease-causing bacteria and fungi. These include bacteria that can cause foodborne illness and that can be life-threatening for HIV patients or those with weakened immune systems [R, R+, R+, R, R, R, R].
One study used a paste containing neem and turmeric to treat 814 people with scabies, and 97% of cases were cured within 2 weeks. However, this study lacked a control group [R].
7) Reproduction and Birth Control
Neem oil is used as a contraceptive in some parts of India. It’s been suggested as a natural and cheap means of population control. It would be especially beneficial for rural populations that don’t have access to other types of birth control. Some consider this may be neem’s greatest untapped potential. But whether or not neem oil is an effective contraceptive is still far from certain [R].
In a study of 242 women, over 95% of those who applied neem oil vaginally as a contraceptive did not become pregnant for at least one year. These women also had fewer urinary tract infections [R+].
Another older study claimed that applying neem oil to the vagina before sex was 100% effective at preventing pregnancy in humans. However, the data from this study–including details like how many people were included–isn’t available, so there’s not much backing up this claim [R].
In monkeys, neem oil applied to the vagina significantly reduced the likelihood of conception. Although studies agree that neem oil applied before mating is effective for preventing pregnancy in monkeys, there is disagreement about whether applying the oil after mating is effective [R, R, R].
An injection of neem oil into the uterus of female rats decreased conception rates for several months, and this effect eventually wore off. An injection into male rats also rendered them infertile, which lasted for the duration of the 8-month study [R, R].
In rodents and primates, neem extracts given early in pregnancy can end the pregnancy [R].
Until high-quality clinical trials are available, neem oil should not be used as a means of birth control; its efficacy and safety are still unclear.
Repelling Insects and Pests
Neem oil applied to the skin can repel mosquitos for up to 12 hours. It can also be burned to repel mosquitos. However, its effectiveness varies somewhat based on the species of mosquito [R, R, R, R].
Neem is also used as a natural pesticide to protect plants and seeds from hungry pests. In labs, neem oil is lethal against multiple pest species, including crop-eating moths and mosquitos [R, R, R, R, R].
Neem oil may be safe to use in dogs. It has also been marketed in products for cats and may be safe at low doses; however, there are reports of neem oil causing dangerous side effects in some cats [R+, R+].
A combination of neem oil applied to the skin and eating neem leaves was as effective as a standard treatment at removing mites from dogs. A neem-containing shampoo was similarly effective at removing mites causing scabies [R, R].
A neem-containing cream was effective at treating a fungal infection in horses [R].
Neem extracts may have a wider spectrum of benefits than the oil (which should not be ingested). The following potential health benefits do not apply to neem oil but only to the extracts prepared from neem leaves. Only extracts can deliver active compounds from neem to the bloodstream.
8) Protecting the Liver, Kidney, Heart, and Brain
Neem improved coordination in rats with nerve damage. Extracts from neem leaves could also protect rat brain cells from damage caused by chemotherapy; neem-treated rats had less brain cell death and showed fewer signs of tissue damage in the brain [R+, R, R].
Similarly, 10 people with HIV were given a neem leaf extract in another study. The extract increased their white blood cell count after one month [R].
In a study of 90 men with diabetes, pills with neem leaf powder reduced diabetes symptoms like tiredness, hunger, and headache. However, the study lacked a control group, making it difficult to rule out a placebo effect [R].
How To Use Neem Oil
Since high temperatures can destroy important molecules like azadirachtin, there is some logic behind the idea that cold-pressed neem oil might be “better.” However, there haven’t been studies directly comparing the health effects of neem oil that has or hasn’t been cold-pressed [R].
In part due to the variety of ways neem can be prepared and consumed, there isn’t a standard dosage.
For extracts, the dosing varies. One study suggested that about 20 mg of one extract per day would be safe, while another used 1 g per day of a different extract and reported no adverse effects [R+, R].
How to Apply
Various cosmetic products contain neem oil while you can also purchase the pure oil. Have in mind that its potency will vary depending on the manufacturer.
Some people are allergic to neem oil. If you plan to use neem oil on your skin, it’s best to do a patch test first. Apply a small amount of the oil on the upper part of your inner arm and wait for at least 24 hours to see how your skin will react [R].
If you don’t develop a skin reaction, you can apply small amounts of neem oil directly to your skin–such as on areas affected by acne. Use sparingly due to its strong bioactive chemicals. This also applies to its use on the hair and scalp.
Alternatively, you can mix neem oil with a base oil, such as coconut oil, olive oil, shea butter, or others. Mix in a small amount of neem oil with your base oil and try it out on your skin or hair. As for the amount of neem oil you should use, have in mind that most cosmetic products don’t contain over 2%.
For hair care, be sure not to mix it primarily with thick oils (such as castor oil), as the mixture will be hard to wash out and may cause hair matting or tangling.
Users of neem products generally report high satisfaction, claiming that it is effective for improving dental health, dealing with acne, athlete’s foot and pain, and repelling mosquitos.
However, many users also urge caution, particularly with more concentrated forms of neem, as high doses can cause unpleasant side effects.
Several users also commented on the smell of neem oil, with descriptions from “distinctive” to “awful.”
Neem oil applied to the skin is typically touted as safe, with many studies claiming that there were no side effects whatsoever–although such claims should always be viewed with healthy skepticism [R+, R+, R+].
Rare instances of allergic reactions to neem oil have been reported, usually resulting in a rash. It’s not clear what part of the oil induces these allergies, so users should be cautious [R].
Neem oil shouldn’t be ingested. There have been reports of neem oil poisoning, particularly in children and the elderly. This is likely caused by azadirachtin and can lead to vomiting, seizures, and liver problems. As such, neem is best avoided or used with extreme caution in these groups [R+, R, R].
Applied vaginally, neem oil can cause genital itching, burning, and stomach pain, though serious side effects are rare. Some studies also reported decreased sexual satisfaction in users’ partners. Neem oil should not be used as a birth control method due to the lack of safety and efficacy data [R, R].
Ingesting neem extracts, rather than applying neem oil to the skin, may affect heart rate, blood pressure, and fertility. Although serious side effects in humans are rare, it’s advisable to be extra careful taking such extracts and to always talk to your doctor before supplementing [R+, R].
In rats, using a neem extract during pregnancy didn’t seem to cause problems in their offspring. However, because it can affect fertility in ways that aren’t totally understood, it’s probably best for anyone who is pregnant or is planning to become pregnant to avoid neem oil and neem supplements [R, R].
Limitations and Caveats
Data on neem in humans is limited, and many of the available studies have serious flaws, including lacking control groups and failing to report important details about treatments. Most human studies were also very small, so it’s hard to generalize their results [R, R, R].
A number of the studies in humans used relatively subjective measurements–like the appearance of acne. Although not necessarily disqualifying, such studies are more susceptible to bias, especially when proper controls aren’t included [R, R+, R+].
Several studies used combinations of herbs including neem. Although herbal treatments were often reported to be effective, it’s impossible to say whether any single ingredient, like neem, would be effective on its own [R, R+, R+].
Buy Neem Oil
The neem tree has been used in Ayurveda and traditional medicine for thousands of years.
Neem oil can also be used to improve the appearance of skin and hair and enhance oral health, although the scientific evidence is limited. Although it might also be a cheap and safe spermicide, more research is needed before its birth control use can be recommended.
Beyond its health applications, neem may be useful as a natural pesticide.
Neem extracts may be beneficial for people with diabetes and they might protect the heart, kidneys, and brain from toxins. Although extracts may have a wider spectrum of health benefits than the oil, they are also much more likely to cause side effects. While neem oil is usually made from the seeds, extracts are prepared from the leaves. Both have some similar active compounds, but their concentrations can vary.
The oil should only be applied to the skin or hair–accidental ingestion can cause poisoning.
Due to the risk of serious bad reactions, neem should always be used with caution, especially in more concentrated pill forms.
Neem oil is probably safe to use on the skin and hair, but it’s best to ask your doctor before supplementing with extracts.