Cannabis has many medicinal applications, including using it to alleviate pain and muscle spasms. Dried buds of the cannabis plant also produce a resin that contains cannabinoids such as THC and CBD which can be used medicinally or recreationally. One method of extraction is to use a solvent, usually butane , to strip some of the cannabinoids out of the plant and into a liquid that can then be evaporated to leave behind the pure resin. This solvent extraction method also leaves trace amounts of toxins in the product, which is dangerous for people with compromised immune systems or respiratory problems.