Castor oil can cause spasmodic contractions (cramps) in the smooth intestinal muscle.
Soft gel capsules of castor oil, when taken with food in adults and children over 12 years of age, provide a mild laxative effect within 1 to 3 hours and can be used to relieve occasional constipation.
Castor oil is sometimes used to induce labor. In pregnancy, when the cervix has partially opened, ricinoleic acid acts on the uterus and can help with labor contractions, but irregular and painful contractions caused by the consumption of castor oil may be stressful for the mother and the fetus.