Question

what are the ingredients inside of lemon peel? can it kill germs and insects?

Answer 1

citric acid is present in lemon

Answer 2

Limonene is a natural insect repellent. Citrus peels contain the extra pest killer linalool, also obtained by extracting oil from the rind. Pests hate limonene and linalool and will avoid areas treated with them. While it may not kill adult fleas, limonene does paralyze them.