Castor oil for constipation is a safe and effective home remedy when used according to directions in over-counter-versions of the oil. Using castor oil for constipation can be so effective in purging the intestinal tract that days will pass before normal intestinal function resumes. The use of castor oil for constipation is possible because it stimulates the walls of the small and large intestines. Castor oil should be used only on a short-term basis, because long-term use can make gastric distress worse. The oil has potential side effects, and it is not recommended for use by nursing or pregnant women because of potential harm to the child.

The castor bean from which castor oil is derived contains ricin, one of the most potent poisons known to man, with as little as 1 milligram being a fatal dose for an adult male. Commercial production of castor oil from castor beans removes the ricin. When using castor oil for constipation, one must consider that the oil can produce pelvic congestion, that it might induce abortions and that the oil can be carried through milk glands to nursing infants. The fatal dose of castor oil is unknown, but is presumed to be quite large. Persons who abuse castor oil for constipation can experience issues such as dehydration and electrolyte imbalances caused by the oil's tendency to decrease water absorption through the intestinal wall.

In ancient Egypt, it was common to use castor oil for constipation. The castor plant is a native of east Africa and was known to this civilization. Since then, use of castor oil for constipation has spread worldwide, and the oil has many uses other than as a treatment of intestinal distress. Castor oil also is used as a flavor enhancer in food production and as a lubricant in many industrial uses. In the early days of the United States castor oil was mixed with alcohol and sold as a remedy for everything from constipation to arthritis, although research has shown that castor oil has no measurable effect on arthritis.