For many centuries, folklore medicine has recommended the use of castor oil, either orally or transdermally, for a wide range of complaints. Naturopathic doctors and other practitioners continue to utilize its therapeutic potential in the management of the health of their patients and clients.

When confronted with the recommendation for topical application by their healthcare provider, many people will baulk and wonder why they should cover parts of their torso with the sticky oil. In medical school we learn this as one of our basic fundamental treatments for any gastrointestinal complaint or painful musculoskeletal malady. I have prescribed topical castor oil to well over 500 patients and have seen it work miraculously. Being both a scientist and a medical individual, I wanted to see if modern science could prove how and why the age-old wisdom of castor oil works. Thus, I dove into the literature to see what was currently understood about its purported mechanisms of action and how we might translate that alongside our therapeutic considerations.

Indications & Mechanisms of action

Castor oil has many potential uses but the most common reasons for considering its application are:

  1. Pain
  2. Inflammation
  3. Swelling
  4. Gas and bloating
  5. Constipation
  6. Detoxification
  7. Fibrocystic breasts
  8. Skin tonification

Castor oil is made from the plant Ricinus communis (castor bean). It has been used since ancient Egyptian times, internally as a cathartic (stimulating laxative) and to induce labor. Topically, it has been used as a wound healer, anti-inflammatory agent, detoxifier, immunomodulator, and has been found helpful in gastrointestinal complaints.1,2 The precise mechanisms of action for this remarkable plant have not been fully elucidated. Most of the traditional uses come from folk medicines and word of mouth in certain traditions around the world.1-3

The main active component is considered to be ricinoleic acid (RA), which exerts analgesic and anti-inflammatory effects.4 RA has been shown to have similar pharmacological properties to capsaicin.5 It is suggested that RA acts on sensory neuropeptide-mediated neurogenic inflammation.4

Although the therapeutic effect in constipation is not fully understood, observational evidence points to its efficacy. A 2011 study6 in Complementary Therapies in Clinical Practice, involving 80% of the subjects who had constipation for more than 10 years, showed that ” [castor oil pack] administration did not have an effect on the number of bowel movements or amount of feces, but decreased the feces consistency score, straining during defecation and feeling of complete evacuation after a bowel movement, thus decreasing symptoms of constipation.”6

Effects on immunity

The leading theory of how castor oil positively affects the immune system is via an increase of T-cells in the skin and augmentation of prostaglandins.7 The T-11 cell increase represents a general boost in the body’s specific defense status.8 Lymphocytes are white blood cells that can be divided into 2 major types: B-cells and T-cells. B-cells make antibodies that attack bacteria and toxins, whereas T-cells originate from bone marrow and the thymus gland and are responsible for attacking and killing a variety of invaders such as viruses, fungi, and cancer cells. T-11 cells are responsible for producing specific antibodies for our immune system. The skin T-cell theory postulates that castor oil triggers T-lymphocytes in the skin, causing them to activate a local and/or systemic immune reaction.7

A well-written and referenced review of 7 castor oil studies by Drs Kennedy and Keaton goes into further detail in their 2012 article titled, “Evidence for the Topical Application of Castor Oil.“9 They refer to a study in which 17 patients with fatigue were given castor oil packs for 2 weeks (5 days each week). “During the course of treatment, the mean total lymphocyte counts normalized within the group and were lower at the end of treatment vs. baseline. As an unexpected outcome, 2 participants with elevated liver enzymes and cholesterol normalized these variables by the end of the study.”9

Although topical clinical and anecdotal observations of castor oil’s efficacy have been noted, the exact biochemical pathways involved are not understood.10 Studies have found little evidence of its topical absorption, raising the possibility that non-biochemical mechanisms are involved in castor oil’s therapeutic effects, such as a vibrational or energy effect.3

Summary

As this review has indicated, castor oil is of potentially high therapeutic value, with low odor, low incidence of side effects, and an overall low-risk profile. Castor oil is highly underutilized in today’s modern medical world, even among my venerable naturopathic colleagues.