Neem oil side effects are very few on both plants and humans alike. Neem is a beautiful substance with uses as varied as a plant pesticide to a hair growth agent. In this article, we will be doing an in-depth yet brief analysis of all the potential side effects that can occur after its use.Neem Oil Side Effects

Find out research-backed information about the adverse impact of this oil on plants, humans, and animals in this comprehensive article.

What Are Some Common Neem Oil Side Effects on Plants?

Some common neem oil side effects on plants are heat and chemical burns when exposed to sunlight and high temperatures. Neem oil can also potentially kill seedlings or lead to stunted growth. It also disturbs the plant’s ecosystem by harming beneficial pests and bugs.

– Undiluted Oil Can Burn Plants

You need to bathe the whole plant with this oil while using it as a pesticide. Oil in its pure and undiluted form will likely cause chemical burns to the plant’s stems and foliage. The plant develops yellow and brown spots that are dry to the touch, which is an indicator that the plant is in a stressful situation.

Undiluted oil also blocks the tiny pores through which plants carry out respiration. The plant ultimately begins to suffocate, which might increase its risk of getting burns. The key reason is that the oil is potent and will be pretty damaging to the leaves if it is not adequately diluted or emulsified.

The risk of getting neem burns increases with the rise in daily temperatures. Plants kept outdoors, under the bright sun, and during the hot summer months get burned quicker and more intensely.

So any neem oil spray that involves soap must never be used on these plants. The same goes for using oil directly without diluting it with water first. If you own carnivorous plants for ornamental purposes, using alternative organic materials other than neem oil is best.

While neem oil is safe for use on some plants generally, you must stop using it at least three weeks before harvesting, and you must dilute it in the right way. The same is true for more or less all plants meant for immediate consumption. Even if you use 100 percent organic oil, it should not be applied if you haven’t diluted it in the right way and the correct ratio.

– It Can Burn Stressed Plants

Plants already under some stress will get burned by neem oil easily and quickly. Examples of stressed plants are plants that are either diseased, recovering, or recently transplanted. If you are using this oil as an insecticide, the plant is likely weak from the ongoing pest attack because the state of the plant is weak already.Stressed Plant Care

That is why you must thoroughly dilute the oil and do a patch test on the plant, and check what the plant is going through. Even if not cut, use only two to three drops of oil in a water-soaked cotton roll.

In summer, the plants and vegetables are most stressed around and during noon time when the temperatures are at their peak. Moreover, remember that oils when used, such as neem foliar spray during this time, will suffocate and burn the plant leaves, and this is because they aren’t healthy already.

In addition, this oil cannot be used every day on any plant. Even if you are using a very mild and diluted solution, you must still use it only once per week and no more than that. Using it once a week as a pesticide and fungicide is just enough when the plant is recovering.

– It Harms Beneficial Pests

Neem oil affects the eggs and larvae of beneficial insects, too, along with harmful ones. These beneficial pests are essential for the healthy growth of a plant. They help break down organic matter in the soil and create pathways for water and airflow.

Some beneficial pests compete with bugs like aphids and mites to keep their population under control. Neem leaves and oil produces a smell repulsive to most insects and bugs. With beneficial bugs, the plants ultimately have a chance to grow properly.

Neem tree and flower oil should not be used on any herb because these insects will be attracted to the flowers on the herbs as well. Whether you are growing cilantro, dill, basil, rosemary, or parsley, try to use a different organic pest control method on these specific plants. In addition, these are sensitive to the strong chemicals present in neem plants and might react negatively to them.

– Leaves a Greasy Residue on Leaves

It is only natural that neem oil will leave a greasy and oily residue all over a plant. Even a few drops of oil will leave the plant glistening for days when used alone or with water. Since oil is not easily washed away with water, you will have difficulty cleaning the plant after using neem extract oil.Apply Neem Oil on Leaves

This oil takes about three to five days before it breaks down on the surface of plants. It is ideal that you would abstain from using it on vegetables ready to be consumed.

Use a neem foliar spray on plants well before harvest so that your vegetables are oil-free when it is time to eat them. Carnivorous plants do not like being bathed with soapy solutions, and this is why the leaves can feel like it the oil is heavy on them. In such a matter, the leaves cannot handle such a case, and so the side effect would be disastrous in this case.

– Might Kill Seedlings

Mature plants and vegetables can resist the side effects of neem tree oil well. Seeds and seedlings, on the other hand, are not so resistant to the few potential harms of this substance. It is also unnecessary to use this oil on seedlings during and after their germination phase.

When seedlings are grown under direct sunlight and high humidity, oil might kill them. Care must also be taken when applying this oil’s solutions around seedlings. Even if these seedlings do manage to germinate, the new plant ultimately suffers in the long term. It might develop foliage of poor quality and suffer from stunted growth.

Neem oil should not be used on seedling herbs because they are sensitive to it and prone to getting chemical burns and would hinder the growth of the herb plant as its ability to continue growing. Vegetables with thin leaves, like lettuce, only tolerate this oil a little.

What Are Neem Oil Side Effects on Humans and Animals?

Neem oil side effects on humans are mainly the development of eczema or allergic skin reactions. When ingested in large amounts, it might adversely affect kidneys and male fertility. In pets, neem will cause abdominal pain and other symptoms such as vomiting and diarrhea.

– Allergic Reactions

Neem oil is generally very safe for humans’ internal and external use. As a potent active substance, it can exacerbate specific individuals’ eczema and related skin conditions. Before using this oil on plants or for your health, do a patch test first. Apply two to three drops of oil on a patch on your elbow and see if an allergic reaction develops.Safely Using Neem Oil

We all know how neem leaf and its extracts are used for various health benefits worldwide. Unless your body is allergic, it can be used for wound healing, dental health, hair health, and various skin problems like acne and head lice.

Neem extract and oil are antibacterial properties and are an excellent remedy for acne-prone skin, but when you have an allergy to this plant, it wouldn’t be beneficial but more harmful. It is also suitable for getting rid of blemishes and acne spots. In short, azadirachtin is an active ingredient in neem that can also irritate the skin in susceptible individuals to cause allergy and eczema.

– Kidney Failure

Oral intake of neem in various forms is a different story altogether. In moderate amounts, this oil can help control the blood sugar levels of diabetics and improve kidney health. However, cases of neem poisoning have been reported when ingested at doses around five to 30 mL. This is an indicator that the oil is a heavy one that the body may not be able to digest it well, if it has sensitivity to it.

Long-term intake of neem leaves, tea, and oil has been linked with kidney failure instead of improvement. People with diabetes using this as a supplement to control blood sugar must consult their doctor before incorporating neem in their diet, but when taken in a different and more intense dose, you will see how it results in a consequence that can be unbearable.

– Decreases Fertility

Regular consumption of neem powder or neem leaf tea has been linked to male infertility cases. Even after a single dose, long-term contraceptive effects have been observed in men. However, there is still a need for more comprehensive research on this, and no evidence of external use producing any such effect exists, but it is more of an internal case.Neem Leaf Tea

– On Pets

Animals, especially household pests, cannot tolerate neem products when ingested. Even in moderate amounts, this can lead to vomiting, nausea, and vomiting in cats and dogs. In larger doses, there is a risk that the poor animal might develop toxicity and a severe allergic reaction. When using this oil as a plant pesticide, take measures so the pests do not lick it off the plants.

– On Vegetables From Your Kitchen Garden

Vegetables with thin and wispy leaves get quickly burned when neem is applied. This goes for neem application, whether as a foliar spray or oil droplets.

This point is especially pertinent when vegetables are grown outdoors under direct sunlight. If your lettuce, spinach, peas, and even when it comes in contact with herbs, have a pest problem, try something other than neem.


To sum up, significantly few side effects are associated with this wonder substance, and you can easily avoid them with just a little effort and caution, in short:

  • Neem oil should be avoided on plants with fragile leaves, like lettuce, because it causes burns. Using neem every day on plants will end up causing chemical burns to their foliage.
  • Some factors that increase the risk of foliage burns are using undiluted oil under direct sun, high temperatures, and using this oil too frequently.
  • Do a patch test on your skin to see if you are allergic to neem. It is ideal to wear thick rubber gloves when applying neem as a plant fungicide or pesticide.
  • To avoid side effects, try to obtain oil from neem flowers that are 100 percent organic and authentic. The bottom line is that neem oil benefits outweigh the few side effects.

Neem oil is a powerful natural product that offers numerous benefits for pest control, skincare, and overall plant health. However, like any substance, it is essential to be aware of potential side effects and use it responsibly.

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