Castor oil has been used for centuries in traditional folk medicine practices and has also been called the “palm of Christ” due to its reported ability to cure various ailments. In contemporary society, castor oil is found in everything from cosmetics to bio-diesel, but it is castor oil’s therapeutic abilities that make it a popular topic for research.

Scientists in New Delhi, India, investigated castor oil’s effects on knee arthritis. The study, published in October 2009 in “Phytotherapy Research,” gave patients either a castor oil capsule three times a day for four weeks or a capsule of diclofenac sodium, a prescription anti-inflammatory drug often used to treat arthritis. After the trial period, both supplements were equally effective at reducing knee arthritis symptoms, although castor oil had none of the side effects associated with the prescription medication.

Castor oil packs are made from several layers of a material such as flannel that are soaked with the oil and placed on various parts of the body with a heating pad on top, presumably to treat a variety of ailments, including sinusitis and headaches. Although few of these uses have been studied, one research project reported in “Complementary Therapies in Clinical Practice” in February 2011 found that castor oil packs helped improve symptoms of chronic long-term constipation in elderly patients.

High cholesterol and elevated levels of triglycerides in your bloodstream increase your risk for getting heart disease or having a heart attack over time. A study in 1999 in “Bioscience, Biotechnology and Biochemistry” found that castor oil fed to rats significantly lowered their cholesterol and triglyceride levels.

Dry eye, also known as meibomian gland dysfunction, is a condition in which glands in your eyelids fail to produce oil and cause irritation and inflammation. In a 2002 issue of the journal “Ophthalmology,” a team of Japanese researchers reported that eyedrops made with castor oil greatly improved dry-eye symptoms compared with a placebo, when given six times a day for two weeks. Note, however, that most bottles of castor oil indicate to keep it away from the eyes, and you shouldn’t use castor oil directly in your eyes without a doctor’s approval.

Castor oil is often used by midwives in some cultures to induce labor, but the practice is controversial, and studies are mixed. One of the largest studies, however, was undertaken in Thailand clinics and involved 612 women with a gestation of more than 40 weeks. The researchers found that castor oil had no effect on time to birth and concluded no justification existed for recommending castor oil for this purpose. There is one reported case of a woman at 39 weeks' gestation who experienced a uterine rupture after taking 5 mL of castor oil.

Castor oil primarily has been used as a laxative, and the Food and Drug Administration classifies it as generally recognized as safe and effective in that role. However, it can work too well, leading to painful cramping, unpredictable diarrhea and fecal incontinence. Long-term use of castor oil can cause fluid and electrolyte loss.