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What are the Most Common Neem Side Effects?

By Tara Barnett
Updated Mar 03, 2024
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The ingestion or topical application of neem, which is an evergreen tree traditionally used as medicine in ayurvedic practices, can cause side effects such as liver and kidney damage, allergic reactions and Reye’s Syndrome. It also is linked to infertility and miscarriage, which can be negative or positive, depending on what a person’s conception wishes are. People also have been reported low blood sugar, vomiting, diarrhea, aggravation of immune system conditions and interference with other types of medications, such as lithium.

Liver and Kidney Damage

Some studies suggest that, because of its natural antioxidant properties, neem can protect both the liver and kidneys when taken in small amounts. These organs serve as the body’s filters, removing waste and toxins. Taken in high quantities or for extended periods, however, this substance can overwork them and cause damage. Common signs of problems with the kidneys and liver include jaundice or yellowing of the skin and reduced urine production.

Allergic Reaction

One of the biggest uses for neem is the treatment of skin conditions, such as eczema and psoriasis. Medical professionals think that it can alleviate symptoms from these types of conditions because it acts as an antifungal and antibacterial agent. As with many other substances, however, individuals sometimes are allergic to it. In some instances, it isn’t clear whether it is the neem or another ingredient in a product that is causing the problem, but allergy testing or switching to a different item often can provide clues. Symptoms of a reaction include rashes, itching, swelling and, in more severe cases, difficulty breathing.

Infertility and Miscarriage

Farmers use neem in insecticides in part because the substance causes infertility in pests, making it difficult for them to reproduce. This same effect can show up in people. Experts believe that it negatively affects the movement of sperm cells, and it also might cause the immune system to become more active, thereby causing a woman’s body to attack the sperm more aggressively or to reject an implanted embryo. For some people, this is desirable, but it is not good for those who are trying to conceive.

Reye's Syndrome

Even though adults are sometimes able to use neem, it is not safe for children because it contains aspirin-like compounds that can cause Reye's Syndrome. This condition results in the abnormal accumulation of fat in body organs and pressure on the brain, with symptoms such as vomiting, fatigue, aggressiveness or irritability, disorientation and coma all possible. It is potentially fatal if left untreated, but when caught early, recovery odds are good.

Immune System Disease Aggravation

When used by itself, or when it appears as an ingredient in other products, neem has the potential to boost the immune system, which many people actually want to prevent getting sick or to combat illness. Individuals who have a medical condition such as arthritis that gets worse when the immune system is in overdrive, however, should avoid applying it to the skin or ingesting it. Its ability to improve immunity also means it can interfere with medications used to treat these types of conditions, reducing their effectiveness.

Low Blood Sugar

In many people, neem side effects include a drop in blood sugar levels, which is one reason why medical professionals occasionally recommend it to control diabetes. The drop sometimes can be too extreme, however, which can lead to problems such as dizziness, headaches, sweating and weakness. More severe symptoms include impaired coordination and concentration, numbness in the mouth, loss of consciousness and coma. As with immune system medications, this substance can reduce how well drugs meant to stabilize blood glucose work.

Other Medication Interference

Organ transplant recipients generally must take immunosuppressant medications for the rest of their lives to keep their immune systems from attacking the transplanted tissues. They typically should not use neem, because its immune-boosting qualities can make it harder for these drugs to work. Studies also suggest that it interferes with lithium, which is most commonly used for mental conditions such as bipolar disorder or schizophrenia.

Additional Side Effects

The antibacterial, antifungal and anti-inflammatory properties of neem are thought to be beneficial to the digestive system, clearing out potentially harmful pathogens and promoting healing. People have used it to treat ulcers, stomach upset and other digestive conditions for these reasons, commonly drinking it as a tea. Some users, however, do not tolerate the chemicals in neem well, and experience vomiting. Others have problems with extremely loose stools, frequent urination or dehydration, because it has a diuretic effect.


Although people have used this plant in various forms as a traditional medicine for hundreds of years, dosing still is not standardized, meaning that it is extremely difficult to assess safety and the potential risk of neem side effects even in adults. It appears that many of the serious health problems tend to occur when the amount consumed or put onto the skin is high, or when someone uses it for an extended period of time. Much of what is in the medical literature and on various websites is not conclusive, and at times, is even conflicting. For these reasons, anyone wanting to use neem should do so under the guidance of a trained medical professional.

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Discussion Comments
By anon1006372 — On Feb 28, 2022

Has anyone had a reaction from just touching the wood? My hands broke out in hives after picking up an item made out of the wood from a Neem tree. I've never been exposed to neem in any form before, and I have also never had a reaction like this to anything in my entire life.

By anon962204 — On Jul 22, 2014

"Ingestion of neem' is a misleading statement. One needs to specify what is meant by "neem". There is neem oil, neem leaves, neem bark, neem flowers. Indiscriminately using the term "neem" is misleading and propagates misinformation. Most studies on the ingestion of neem were done with neem oil and in rodents, that should be pointed out too. No studies to date have shown adverse effects for topical uses of neem oil, leaves, or bark. Although, as with all natural or synthetic substances, one can develop allergies.

By rkm12345 — On Jul 16, 2014

I used to take Neem leaves (about 30 leaves) plus six leaves of Tulsi with one Karela, all put together with a glass of water into the Mixi and then after grinding it for two or three minutes, I drink it early in the morning on an empty stomach. Is it all right to take this mixture? Please advise. I have high blood sugar.

By anon958903 — On Jun 30, 2014

I have used neem thrice a weak and my sugar level is normal.

By anon342082 — On Jul 17, 2013

Neem capsules (found in health food stores) are to be taken internally. Neem has antibacterial, antiviral and antifungal properties. Neem (and Reshi) are always in my vitamin cabinet. They are my go to remedy for colds. When we get colds, we take four to six capsules four to six times a day and they never fail to break up congestion.

I'll take them every hour when I get a bad cold (I'll take them at night every time I wake up) and within 24 hours, the congestion is breaking up and I'm feeling better.

By anon334530 — On May 13, 2013

Good to know guys. I suggested a friend of mine to drink it and she said it's having side effects including a reduction in her eyesight. Could that be true?

Can someone explain? It's vital for me to know. Please help.

By anon315392 — On Jan 23, 2013

I disagree with the statement claiming Neem is dangerous, as in the Indian Subcontinent, many people including children use the soft twigs of Neem for brushing their teeth, and as per ayurveda, eating a few Neem leaves is recommended.

By anon308079 — On Dec 08, 2012

I have tinea versicolor on my skin that makes it itch during exercise and that brought my attention to neem capsules. To my understanding, Tinea is a fungal disease on the skin and creams and other meds haven't helped.

By anon294123 — On Sep 29, 2012

To the author of this post and others who have replied. This article fails to mention the difference in neem supplements. Any person familiar with herbal use knows that different parts of some plants have different uses. Neem seed oil is meant for external use only. Taking neem seed oil extract internally is an idea best not acted on. The seeds can be very potent. Neem seed extracts also should be processed in a particular manner. The seeds have a different spectrum of biochemicals than the leaf and bark.

The leaf and bark powder or extract are what you can take internally. Studies and traditional use have found many supportive benefits consistent with neem consumption. One of the benefits of neem leaf and bark is it supports liver health. Neem leaf and bark has been used in India for hundreds of years and it has been used for children. Do you know anyone from India? Have you ever had a discussion about neem with them?

There is a lot to know about all the plants that cover this earth. Please do not let ignorance of others feed a fear that keeps you from learning the truth. When some people are ignorant they use that to feed fear in others. This is used as a tool to win people to a particular side of an issue. I would love to see more people having proper information or guidance in this area. People need better solutions then what chemicals and pharmaceuticals are offering.

More in depth information is available but it is not free. Those who know it in this country have their hands tied to be able to legally share it with you in a normal conversation. Most of the people who could legally share it with you don’t know or have too much money invested in the contrary interest of global power.

I know this sounds a bit crazy but it is not. I would love to see people getting help. I would love to see the freedom of that help being easily available to everyone, no matter if they are invested in a medical institution or a homeless person on the street. --With love, A thoughtful citizen.

P.S.: If you already have a healthy reproductive system, yes, if you discontinue use you will still be able to get pregnant. By healthy, I mean you were able to have children before. Please make sure it is completely out of your system before you attempt to get pregnant. I believe four to six months should be good, depending on diet and activity level.

By Azuza — On Sep 10, 2011

@indemnifyme - I'm a big fan of herbal and natural medicine myself. It always kind of bugs me that the side effects for those aren't listed on the box like with regular medicine.

However, I guess that's what the Internet is for. I think it's generally a good idea to do some research before you take any kind of medicine-natural or from the pharmacy. For instance, my doctor prescribed me a medication for my asthma a few years ago that I decided not to take. After I did some research, I decided the benefits didn't outweigh the risks.

By indemnifyme — On Sep 09, 2011

I've used neem before and I must admit the beginning part of this article really scared me! However, it sounds like you would have to take a much more than the recommended dose to experience the side effects.

Even after reading this, I think I will still use neem in the future. My herbalist recommends it sometimes for when I get sick. Of course, she recommends it like an antibiotic-you take it for 7-10 days and then stop. I've never heard of neem being recommended for long term use.

Also, I'd like to point out that antibiotics and other medicines deemed "safe" by the FDA can have some pretty disturbing side effects as well. Next time you get something from the pharmacy, take the time to read the insert. You might be surprised at what it says!

By candyquilt — On Sep 09, 2011

I'm so glad that there is a site which talks about the side effects of neem. I have been hearing a lot about neem lately. I first heard about it on a TV show about health. They were talking about how neem is a great antioxidant and strengthens the immune system. The brands I've looked at also say all good things about neem- how it's great for skin, how it's safe for pets and how it's completely non-toxic and safe to use in any dose.

Of course it is not as safe as these companies claim. First of all, how could it be safe in any dose when neem directly affects the liver and kidney? My doctor told me that neem should only be taken according to the recommended dose and not more than a couple of months. I think these breaks are required to allow the liver and kidney to recuperate, even though companies never mention of this.

I also highly doubt that neem is entirely safe for pets because it is not safe for children. I think it could affect small pets and animals in the same way.

My friend who has been using neem for her eczema also had to stop taking it because she found out that neem is a blood thinner. She has to take aspirin regularly and her doctor told her not to take them at the same time as it could be dangerous.

After I mentioned about neem to my cousin, she also asked her doctor who said that neem is like an antibiotic and should be used with care just as antibiotics are!

I think that since neem products are not sold with prescription, their side effects are not always listed on the product. That's why I'm glad I had the opportunity to learn about it before I used any. Again, thanks for such a great article and for keeping the public informed!

By discographer — On Sep 08, 2011

@feruze-- Yes, neem prevents pregnancy while it is being used, it's not a permanent change. As far as I know, there have even been some initial studies done on it and scientists are considering using neem as a contraceptive.

Some men and women already take neem extract capsules for this, although I don't think there's any guarantee that it will be 100% effective. Once you stop taking it, you will be back to your normal capacity to conceive, so there is no damage to the reproductive organs or anything.

I would imagine if people used it for a long time or in large doses as a contraceptive though, they might experience some of the other more dangerous side effects. I personally think that until a safe and tested neem contraceptive product is released, people who use neem for its contraceptive effect are doing it at their own risk.

By bear78 — On Sep 08, 2011

Does neem make men impotent permanently or permanently prevent women from getting pregnant?

I have heard of other natural herbs and oils being used as a contraceptive, but usually these are temporary side effects. If you stop using them, you will be able to get pregnant again.

Is neem different?

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