Castor is a plant that produces seeds (beans). Castor oil is produced by pressing ripe seeds that have had their outer covering (hull) removed. The hull contains a deadly poison called ricin. Castor oil has been used as medicine for centuries.
Castor seeds without the hull are used for birth control, constipation, leprosy, and syphilis. Castor oil is used as a laxative for constipation, to start labor in pregnancy, and to start the flow of breast milk.
Some people apply castor seed paste to the skin as a poultice for inflammatory skin disorders, boils, carbuncles, pockets of infection (abscesses), inflammation of the middle ear, and migraine headaches.
Castor oil is used topically to soften skin, bunions and corns; and to dissolve cysts, growths, and warts. It is also applied to the skin for osteoarthritis. Some women put castor oil inside the vagina for birth control or to cause an abortion. Castor oil is used in the eyes to soothe membranes irritated by dust or other materials.
In manufacturing, castor seeds are used to make paints, varnishes, and lubricating oils.