Is neem oil safe to use?
Does neem have side effects?
Neem toxicity, or neem safety to word it positively, is a fairly simple issue.
It can be summed up in a few points:
(And those three points are in the footer on every page on my site.)
Neem use is safe, provided you...
Is neem oil spray safe
And if you are, or hope you soon will be, pregnant, you may also want to know how and why neem may harm you or your child. So let's look at the details.
Several small studies into neem side effects (sources) showed different results.
Some studies suggest that neem should be used with caution. Several neem extracts did show negative side effects when fed to laboratory rats in daily high doses over an extended period of time.
In other studies there were no side effects from neem products (including neem oil) at all, even when using large amounts, and over several generations. (Note: the studies used laboratory rats, not people...)
There is increasing interest in the use of neem as a safe contraceptive. The research here focuses on neem oil, which shows the strongest effect.
But neem bark and neem leaf may also make conception less likely when you take them internally. They stimulate the immune system, and the increased immune system activity is thought to be responsible for the contraceptive and even abortive effect of neem oil.
(More on this page: Neem And Birth Control/Neem Oil As A Contraceptive)
In short, even if there is no hard data, why take chances? Don't take neem if pregnant or trying to conceive. (You can still use neem soap, neem shampoo, lotions, etc.)
This is a common concern of pet owners. Especially cats, which forever clean themselves, ingest whatever you spray them with.
Some studies on laboratory rats did show negative neem side effects (again mostly related to reproduction) when neem seed oil was taken internally. Those rats were fed considerable amounts of neem oil on a daily basis. The neem side effects were reversible, meaning they disappeared when the animals stopped taking neem.
I would not treat any animals that are pregnant, or that you are trying to breed. Otherwise the use of dilute neem oil products (including neem soap and neem shampoo) on pets is considered safe.
The EPA (US Environmental Protection Agency) says neem is Generally Recognized As Safe (GRAS) for use in food products. They even exempted their typical requirement for maximum pesticide residues on agricultural products.
If there are no restrictions regarding maximum allowable residues for farmers, then you also don't have to worry about residues from your neem spray in your vegetable garden. Yes, neem spray is safe. A heck of a lot safer than all the other sprays you ingest with conventionally grown produce!
There is no data or experiences that indicate any negative side effects from using fresh or dried neem leaves (unless you are pregnant/trying to conceive). But any medicinal herb should be ingested with caution. Also, please do take note of the warnings on that page regarding neem extracts. Neem leaf is not the same as leaf extract.
Apply common sense, only take neem leaf in moderation, and start with little when trying it for the first time.
For those who want to dig deeper and read all the scientific details of the individual studies, links to sources are below. You can find more by going to the National Library of Medicine of the National Institutes of Health. Just enter "neem" (plus additional keywords) in the search box and go for it.