Capsaicin
Capsaicin is an animal repellent that has also been registered for use as an insecticide, miticide, rodenticide, and feeding depressant. Capsaicin is obtained from peppers which are the fruit from plants in the genus Capsicum. Capsaicin was first registered for use in the United States in 1962. It is classified as a biochemical pesticide due to its mode of action and the fact that it is a naturally occurring substance.
The peppers are ground into a fine powder. This may be further reined to the oleoresin, which is a reddish-brown liquid with little odor. When extracted from plants, the capsicum oleoresin may contain many volatile compounds in addition to capsaicin.
In addition to its use as a pesticide, capsaicin is used in law enforcement and as an ingredient in cosmetics. Medical researchers have studied capsaicin and its interaction with the TRVP1 receptor for use in pain management. Capsaicin also has been evaluated for treatment of some cancers.
Chili Powder: Though it seems odd that capsaicin, the substance that gives chili peppers and chili powder their fiery heat, would act as a pain reliever, it has indeed been used for years as a topical cream to help people with arthritis, shingles, and psoriasis. Experts suspect 