Neem is a tree grown probably first grown in India. For centuries, its bark has been an effective toothbrush, because, anecdotally, it has been shown to decrease dental decay and to have antiseptic properties. Most medicinal claims regarding its use have not been subject to double blind clinical trials, so all possible benefits of neem should be considered as conjecture.
Portions of the neem tree have been used as an anti-fungal, to remove lice, as a gel to prevent pregnancy, and in oral form to reduce fertility in men. The oil has been added to toothpastes to prevent gum disease and tooth decay. It is also thought to provide some relief to people who suffer from psoriasis, and it may be an effective insecticide.
Others claim that neem may reduce cholesterol, or help rid the body of bladder stones. It also is considered helpful to relieve itching caused by chicken pox or measles. Others might use its extracts to treat ear infections, or pinkeye. Some suggest using neem to treat piles or fistula caused after childbirth, but such used is not recommended.
Use of neem is contraindicated in pregnant women or nursing women, and it should not be used on children. Extracts from the tree have been linked to extreme allergic reactions in children that have caused death, so any products containing neem should be kept far away from children. They should avoid toothpaste containing extracts or oils as well, since they are more likely to swallow the paste.
People may use neem oil, seeds, or leaves, depending upon their intended purpose. Eating the seeds in large amounts would poison someone, and they can cause death. Some people prepare cooked leaves, which are considered to be good for intestinal health, but these have a markedly bitter taste and are not universally enjoyed.
Neem can interact with prescription and over-the-counter medications. Its use should always be discussed with a healthcare professional. Neem may ultimately prove a useful medicine, but more studies need to be performed to understand safe dosage and possible drug interactions. As it stands now, unless guided by a medical professional, most people should probably avoid using products from this tree.