Although neem leaf powder is typically safe with few negative effects, it may cause renal and liver damage if used in excessive quantities. Drinking tea made from the leaves may also cause a rash to develop on your skin, especially if you are allergic to latex. People who are allergic to neem may have problems after taking neem products. Symptoms may include hives, nasal congestion, wheezing, or an itchy throat. If you experience any of these symptoms, contact your doctor immediately. Neem oil has natural insecticidal properties that can be used as a household spray for ants, bugs, and other pests. It is not recommended for use on people because there could be adverse effects such as skin irritation or allergies. Neem oil should not be ingested orally. Neem fruit juice has been shown to be effective in killing bacteria that cause tooth decay. However, its effectiveness as a probiotic is still being studied. To make neem powder, simply dry the neem leaves thoroughly before grinding them into a fine powder. The powder can then be stored in a sealed container for up to one year. There are several brands of neem products available in stores today.