Castor oil is a thick, odorless oil extracted from the bean of the tropical flowering shrub Ricinus communis. It has been historically used to relieve constipation, stomach aches, colds, fever, as an eye lotion, and to induce labor. Currently it is used as a laxative and as an emollient in cosmetics and personal care products, drug delivery systems and wound dressings ^(1) (2). Castor oil is approved by the FDA for safe and effective use as a stimulant laxative.

In preclinical studies castor oil demonstrated antioxidant, antimicrobial, antiviral, anti-inflammatory, wound-healing, antinociceptive and cytotoxic effects ⁽¹⁾. Limited clinical data suggest benefits for eye diseases ⁽³⁾, knee osteoarthritis ⁽⁴⁾ and a meta-analysis determined it can potentially improve the completion rate (CR) and polyp detection rate in colon capsule endoscopy (CCE). The authors suggest it should be actively considered as a viable component for bowel preparation alongside other emerging laxative regimens ⁽⁵⁾. Studies also support use of castor oil for inducing labor  ^{(6) (7) (8)}.

Castor oil and Cancer

Centuries ago, castor oil was among the treatment options for breast cancer that was attributed to an excess of black bile by the Greek physicians Hippocrates and Galen ⁽⁹⁾. Castor oil packs were also popularized in the 1920s by Edgar Cayce, a self-proclaimed psychic and faith healer, to eradicate tumors near the breast surface ⁽¹⁰⁾.

More recently, a castor plant fruit extract showed antiproliferative activity against breast cancer cell lines in vitro ⁽¹¹⁾ and a castor oil extract had a suppressive effect on S180 body tumors and ascites tumors in murine models ⁽¹²⁾. 
According to a case report, a formulation containing Balsam Peru, trypsin and hydrogenated castor oil  accelerated wound healing in a breast cancer patient following radical mastectomy ⁽¹³⁾. But there are no studies in humans that show castor oil has anti-cancer effects.