The seeds of Azadirachta indica—AKA Indian lilac, neem tree, or margosa—contain a useful natural product called neem oil. It has a range of health applications, from moisturizing and conditioning skin and hair, to reducing scalp itching and dandruff, to promoting tooth and gum health.
Impressively, it's also a potent natural pesticide, not because it kills on contact, but because it triggers hormone changes that can disrupt the biological processes of insects.
Finally, the anti-fungal compounds nimbin and azadirachtin make neem oil a powerful cleaning agent. You can mix into a shampoo for your carpet, or dilute it with water (about one tablespoon of oil for each cup of water) and spray it on mattresses or furniture to kill microbial pests.