Castor oil is generally used as an addition to any cosmetic formula and is rarely used as a carrier oil by itself. Extracted from the seeds of the castor oil plant, this oil is very thick and viscous so a little goes a long way. Because of its thickness, castor oil is often used in cosmetic products that require a natural shine or thickness such as nail polish, lipgloss and lipstick. The castor bean contains ricin, a toxic chemical (a tiny amount can kill a human being) but thankfully this isn’t extracted into castor oil.