A Systematic Review
Deborah A. Kennedy, MBA, ND,1,2,3 Dana Keaton, NMD, LAC4
Background: Castor oil has been used for centuries in medicinal and nonmedicinal applications. By far, the most common use is as a cathartic to treat constipation. However, castor oil has also been administered topically, and it is the evidence associated with the topical application of castor oil that is the focus of this review.
Methods: PubMed, Embase, Alt-Med, and CINAHL databases were searched using the terms castor oil/therapeutic use, ricinoleic acid, and Ricinus communis/therapeutic use, not ricin, from inception to July 2009.
Results: Seven studies investigated the topical use of castor oil through direct application of the oil or in the form of castor oil packs.
Conclusions: Preliminary evidence suggests that castor oil may modulate white blood cell count and may have a positive effect on liver function and cholesterol levels; further research is needed in these areas. The topical application of castor oil has been shown to reduce the pain of neurogenic inflammation and to lubricate the eyes as artificial tears.
Castor oil has been used for centuries, and reports of its applications span the globe. A 1982 survey documented uses of the castor oil plant in as many as 50 countries,1 and ancient use of the oil dates back to the 16th century bc.1-2 The oil has had medicinal and nonmedicinal applications throughout history. Uses of castor oil include as an engine-lubricating agent during World War I, in the cosmetics industry, as a food additive, and as an adjuvant in the delivery of some pharmaceutical drugs.3-4 By far, the most known use for castor oil is as a cathartic to treat constipation.1
Castor oil, also known as Palma Christi, is derived from the bean of the plant Ricinus communis, a member of the Euphorbiaceae family, through cold mechanical pressing.2-4 Ricinus communis is native to India, and approximately 90% of the oil is produced in Brazil and India.3-5 The cold-press process yields approximately 33% medicinal-quality oil, which is further refined to rid the oil of ricin, a toxic substance.3-5 Castor oil is composed chiefly of ricinoleic acid, which represents approximately 80% to 90% of the total fatty acids; other fatty acids include oleic acid and linoleic acid.2
Castor oil has a history of medicinal use involving topical applications. It is the evidence associated with the topical application of castor oil that is the focus of this review.
PubMed, Embase, Alt-Med, and CINAHL databases were searched using the terms castor oil/therapeutic use, ricinoleic acid, and Ricinus communis/therapeutic use, not ricin, from inception to May 2011. The result set in PubMed was limited to English language–only articles. The limits for the Embase search were set as English-language topical and articles, journals, or reports. For inclusion in the review, articles had to be related to the topical use of castor oil. Articles dealing with castor oil used in manufacturing, as food additives, or as a cathartic were excluded, as was the use of castor oil to aid in the delivery of pharmaceutical drugs.
Nine studies investigated the topical use of castor oil through direct application of the oil or in the form of castor oil packs. A flowchart of the search strategy is shown in the Figure 1.
Figure 1: Search Strategy Flow Chart
Mein et al6 conducted a small study to assess castor oil absorption through the skin vs oral intake. Epoxydicarbylic acids are the breakdown metabolites of castor oil that are excreted in urine. In a 2-phase study, 3 healthy participants used abdominal castor oil packs with heat for 1½ hours each day for 3 consecutive days. Urine samples were obtained before the start of the phase and were then collected for 8 hours after application of the packs. After a 1-week washout period, castor oil was administered orally; the first dose was 2.5 mL, and a second dose 1 week later was 15 mL. Urine samples were collected. Results indicated no differences in urinary excretion of epoxydicarbylic acid before and after application of castor oil packs. However, significant differences were found before and after oral administration of castor oil. The authors speculate either that castor oil is not well absorbed by the skin or that there is another biochemical pathway of metabolism that remains to be determined.
Maier and colleagues7 assessed the effectiveness of 3 types of contact media (ultrasonographic gel, petroleum jelly, and castor oil) in extracorporeal shock wave application. Patients’ experiences of pain were evaluated during treatment for tendinosis calcarea of the shoulder, radiohumeral epicondylitis, or plantar heel spur. Sixty patients were included in the study, and each patient received 30 treatments (10 each using ultrasonographic gel, petroleum jelly, or castor oil). The patients were blind to the contact media used and were asked to assess their pain using a visual analog scale ranging from 0 (no pain) to 100 (intolerable pain). The study investigators found that the use of castor oil resulted in significantly less pain compared with ultrasonographic gel in all 3 conditions, and visual analog scale scores were lowest with castor oil across all groups. The experience of pain during extracorporeal treatment is due to the formation of cavitations in the skin that irritate the nerve fibers and cause pain. Because of its chemical structure and viscous nature, castor oil does not promote the formation of cavitations in the skin, and it is this feature that the authors attribute to the reduction in pain sensations afforded by castor oil.
In a series of experiments in mice and guinea pigs, Viera et al8-10 investigated the antinociceptive and anti-inflammatory effects of castor oil compared with capsaicin. These investigations involved assessing the responses to painful stimuli, the effect on carrageenan-induced edema, and the degree of irritation from the topical application of ricinoleic acid or capsaicin. Results of the studies demonstrated that ricinoleic acid was devoid of irritant or nociceptive effects from topical applications (unlike capsaicin) yet exerted a potent antinociceptive effect in several tests.10 Ricinoleic acid depletes substance P in the presence of neurogenic inflammation, as does capsaicin.9 Furthermore, capsaicin and ricinoleic acid were anti-inflammatory.8, 10 Aside from its irritating properties on initial application, capsaicin has been found to be effective in the treatment of neuropathic pain; the authors propose that ricinoleic acid may be equally effective (but without irritation) for use in the treatment of cutaneous disorders such as post herpetic neuralgia, diabetic neuropathy, and other neuropathic disorders.9
Immune System and Liver Function
In 1998, Grady11 reported the results of a controlled double-blind study on the effect of the single use of a castor oil pack vs a paraffin oil pack among 36 healthy adults. The packs were applied over the liver and abdomen for 2 hours with heat. Blood samples were collected just before application of the pack (0 hours), 2 hours later after removal of the pack, and at 7 hours and 24 hours. The blood samples were assessed for total lymphocytes, T11 cells, T4 cells, T8 cells, and B cells at each interval. Results of the study indicated that the total lymphocyte count peaked at 7 hours, with an increase in T11 cells contributing to the overall increase in lymphocytes. At the 24-hour mark, total lymphocytes declined, although they remained within normal limits.
In a second study,12 seventeen participants with “fatigue” were recruited to participate in an investigation of long-term use of castor oil packs. Participants applied the castor oil packs for 1½ hours per day over the liver area for 5 days per week for 2 weeks. Blood samples were drawn on days 0, 8, 15, and 22. The blood samples were assessed for total lymphocytes, T11 cells, T4 cells, T8 cells, liver function variables, and cholesterol level. 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 levels normalized these variables by the end of the study.
Constipation can occur at any age, however, the elderly are particularly susceptible. Often they are on multiple medications, have reduced mobility, and insufficient dietary intake.13 Arslen and Eser evaluated the effectiveness of castor oil packs (COP) applied to the abdomen on the symptoms of constipation in 35 nursing home residents over 65 years of age with chronic constipation of over 7 years duration.13 Symptoms of constipation were tracked for 14 days using both a Defecation Monitoring Form and Visual Analog Scale. The following endpoints were assessed: number of bowel movements, amount of feces, fecal consistency, degree of straining and feeling of complete evacuation. The castor oil packs were applied to the abdomen for 60 minutes on 3 consecutive days, Days 8, 9, and 10, of the study. They found that the application of COP to the abdomen resulted in improved fecal consistency, a reducing in straining and improvement in evacuation however, there was no change to the frequency of bowel movements nor the amount of feces evacuated.
Goto et al14 developed low-dose (2%) homogenized castor oil eyedrops for use in noninflamed obstructive meibomian gland dysfunction. In a double-blind placebo-controlled crossover study involving 20 patients (40 eyes), low-dose castor oil eyedrops, or artificial tears, were used twice daily for 2 weeks. After a 2-week washout period, the groups were crossed over. Treatment with castor oil demonstrated improvement in symptoms and in objective findings.The work of Goto et al was further substantiated in a study by Maissa et al. These researchers found that eyedrops containing castor oil produced a more stable tear film and significant decrease in ocular dry eye symptoms.15
The toxicology of castor oil or of formulations of its main constituent, ricinoleic acid, has been evaluated for internal and external use, generally demonstrating castor oil to be nontoxic.4 Case reports in the literature document evidence of contact dermatitis from castor oil in cosmetic products.16-19 None of the studies presented in this review reported any sensitivity reactions to the topical application of castor oil. The absence of local skin effect was a notable observation in a study by Vieira et al.9
Historically, castor oil has been reputed to provide relief for dermatologic conditions, contusions, and inflammatory and ocular disorders. In naturopathic circles, castor oil is used in the form of castor oil packs for varied applications.1, 6 Our review disclosed no cohesive evidence regarding the mechanism of action of castor oil or its main constituent, ricinoleic acid. Investigations by Vieira et al9 demonstrate antinociceptive and anti-inflammatory effects, in part through local depletion of substance P.
Castor oil pack studies show a temporary effect on the immune system that seems to be maintained through consistent use of the packs but is not sustained. The specific mechanism of action remains unknown. Grady11 speculated that castor oil exerts its effects through the activation of prostaglandins. Equally notable is the preliminary evidence that castor oil packs may have a positive effect on normalizing liver enzymes and cholesterol levels. and improving symptoms of constipation12,13 How this occurs, as well as the influence on the immune system, has yet to be elucidated in light of the study by Mein et al.6
Much remains to be explored and confirmed regarding the topical application of castor oil. However, some historical uses for castor oil are substantiated by the evidence presented in this review. Preliminary evidence suggests that castor oil may modulate white blood cell count and may have a positive effect on liver function and cholesterol levels; further research is needed in this area. Castor oil packs may provide a low-cost yet effective means to address cardiovascular disease and liver disease and to maintain lymphocyte counts during chemotherapy. The topical application of castor oil has been shown to reduce the pain of neurogenic inflammation, improve symptoms of constipation and to lubricate the eyes as artificial tears.
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14. Goto E, Shimazaki J, Monden Y, Takano Y, Yagi Y, Shimmura S and Tsubota K. Low-concentration homogenized castor oil eye drops for noninflamed obstructive meibomian gland dysfunction. Ophthalmology. 2002; 109: 2030-5.
15. Maissa C, Guillon M, Simmons P and Vehige J. Effect of castor oil emulsion eyedrops on tear film composition and stability. Cont Lens Anterior Eye. 2010; 33: 76-82.
16. Sanchez-Guerrero IM, Huertas AJ, Lopez MP, Carreno A, Ramirez M and Pajaron M. Angioedema-like allergic contact dermatitis to castor oil. Contact Dermatitis. 2010; 62: 318-9.
17. Shaw DW. Allergic contact dermatitis from 12-hydroxystearic Acid and hydrogenated castor oil. Dermatitis. 2009; 20: E16-20.
18. le Coz CJ and Ball C. Recurrent allergic contact dermatitis and cheilitis due to castor oil. Contact Dermatitis. 2000; 42: 114-5.
19. Taghipour K, Tatnall F and Orton D. Allergic axillary dermatitis due to hydrogenated castor oil in a deodorant. Contact Dermatitis. 2008; 58: 168-9.