Neem Oil has been used for hundreds of years to control pests and diseases. These include toothpaste, cosmetics, soaps, and pet shampoos. Azadirachtin is the most active. It reduces insect feeding and acts as a repellent. It also interferes with insect hormone systems, making it harder for insects to grow and lay eggs. Azadirachtin can also repel and reduce the feeding of nematodes. Other components of neem oil kill insects by hindering their ability to feed.