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While castor oil is becoming a popular home remedy for hair, detoxification, and skin health, its use predates modern medicine. Traditionally, it is used as a hair oil in Indian and African cultures. In ancient Egypt, castor oil was used for cervical ripening and labor induction. In the 1800s, castor oil was used by doctors for the treatment of urticaria, constipation, eczema, rosacea, tonsilitis, and more. In modern medicine, castor oil is used as an adjuvant for drug administration, polymer, packaging ingredient, sealing agent, and component of implants and injectable gels. There are also examples of its use outside of medicine as a lubricant for engines during World War I, fuel and biodiesel, fertilizers, soaps, lubricants, waxes, furniture coatings, brake fluid, and hydraulic fluid. Castor oil has a plethora of uses. But does it work as a therapeutic agent in human health, or is it purely anecdotal?

Castor oil is produced by cold-pressing the seed of the Ricinus communis plant. It is primarily composed of glycerides of ricinoleic, isoricinoleic, stearic, dihydroxy-stearic, eicosanoic, linolenic, linoleic, and palmitic acids. Although cold-pressing only produces a 45% yield (compared to an 80% yield from high-heat processing), this approach produces an oil that is lower in acid and iodine content. During processing, ricin, a toxin found in castor beans, is removed from the oil.

Why is castor oil thought to be a “cure-all”?

Castor oil is considered beneficial for its anti-inflammatory, antimicrobial, analgesic, antioxidant, wound-healing, vasoconstrictive, and anti-nociceptive properties. Castor seeds generally produce a high-yield crop, making it an accessible and affordable resource. In skin and hair care, the fatty acid content of the oil is considered useful as a moisturizer, cleanser, and hydrating agent. It is also thought to benefit hair growth by improving scalp health and reducing dandruff. With so many uses, castor oil may be an inexpensive and natural option for personal care.

Unfortunately, much of the research involving castor oil and its reported uses is of poor quality or lacking. A 2013 systematic review on the use of castor oil for labor induction found that sample sizes from three clinical trials were too small to make any conclusions. While castor oil is considered a powerful cathartic, it is not yet clear if it can induce labor. For the individuals in these trials, the most common side effect was nausea when ingested. A 2022 systematic review ultimately found that there is weak evidence to support the use of castor oil for hair growth, hair quality, or infestation (e.g., with head lice). While castor oil has centuries of anecdotal evidence touting its benefits, it may not improve human health as much as previously thought.

What does the research say about potential uses?

Although evidence is largely lacking, castor oil may be efficacious in some instances. Below is where the research currently stands on the uses of castor oil.

• Hair growth: There is weak evidence supporting the claim that castor oil improves hair growth or quality. However, the ricinoleic acid content of castor oil may be a promising treatment for hair growth in individuals with androgenic alopecia. A more recent systematic review from 2020 suggests that while castor oil may be helpful for alopecia, other oils (e.g., olive, rosemary, tea tree, thyme, lavender, evening primrose oil, and cedarwood oils) may be more effective.
• Constipation support: Of the reported benefits, the laxative effect of castor oil is one of the most supported claims in the literature. Because of castor oil’s efficacy as a laxative when ingested, it can help prepare individuals for MRI scans. To mitigate potential errors on MRI scans of the abdominal region, castor oil is a safe and effective stimulant to clear the colon. A 2011 study on elderly patients assessed whether castor oil packs can help alleviate constipation. 80% of study participants had been struggling with constipation for at least 10 years. Researchers found that, while castor oil administration did not affect the number of bowel movements or the amount of fecal matter, it did decrease the feces consistency score (i.e., 0 = “normal”), reduced straining, and improved the feeling of evacuation after a bowel movement. This study suggests that castor oil may help control the symptoms of constipation. However, it’s worth mentioning that constipation support should include dietary intervention (i.e., increased fiber) and lifestyle support, along with diagnostic testing for colorectal malignancies and diseases before administering castor oil under the supervision of a doctor.
• Skin health: Because of the antimicrobial and anti-inflammatory properties of castor oil, it is thought to help prevent acne and blemishes of the skin when applied topically. Furthermore, the fatty acid content may also support skin softening and texture improvement. However, more research is required to elucidate the efficacy of castor oil in skincare. Where castor oil shines is its use in Traditional Chinese Medicine (TCM) integrated photo-responsive microneedles, which are used to treat autoimmune diseases, such as systemic sclerosis. In TCM, castor oil is revered for its triacylglycerol composition. Microneedles tipped with a castor oil-containing solution may decrease the deposition of collagen, improve skin fibrosis, and decrease epidermal thickness. They may also support inflammation associated with lesions of the skin associated with autoimmunity.
• Eye health: Castor oil has promising uses for treating symptoms of eye conditions. Individuals with meibomian gland dysfunction and dry eye disease may struggle to find therapies that target the conditions. When castor oil is applied to the eye, it may improve condition symptoms by increasing tear film. Additionally, in cases of blepharitis, castor oil applied to the eyelid appears to improve the ocular surface and reduce symptoms. More studies with longer follow-ups after treatment are required to understand the long-term effects of castor oil application in the eye or on eyelids.
• Arthritis & nerve pain disorders: A 2009 randomized, double-blind, comparative study evaluated the efficacy of castor oil in the treatment of osteoarthritis. Participants were given a castor oil or diclofenac sodium capsule three times daily for 4 weeks. At the end of the 4 weeks, both treatments were found to significantly improve symptoms. However, adverse drug reactions were observed in the participants taking diclofenac sodium, whereas participants taking the castor oil capsules did not report any adverse effects. A mouse study from 2000 found that ricinoleic acid may have uses for pain reduction in neuropathic disorders, but the mechanisms require further research. Topical application may have additional benefits for pain and inflammation, but more research is required.
• Treatment of head lice: Infestation may be remediated by castor oil. A 2010 prospective cohort study of 108 patients with head lice infestation assessed whether a castor oil-containing spray was beneficial in treating the condition. Patients were sprayed with the silicon oil spray that contained dimethiconol and castor oil. Researchers wanted to test the pediculicidal (killed all lice after 1 hour, still dead at day 1) and ovicidal (stopped larval growth stages at days 1 and 7) effects. 91.7% of patients had a pediculicidal effect at 1 hour. 87% of patients showed a pediculicidal effect at day 1. 73.6% of patients showed an ovicidal effect at day 7. A second application on day 8 increased efficacy to 79.6%. More research is needed; however, the efficacy of this spray is similar to that of pesticides malathion and permethrin. If individuals are fearful of pesticides, this spray is a safer alternative with potentially equal efficacy.
• Wound healing: A 2022 study showed promising uses for castor oil in wound healing when combined with curcumin on a wound cover. When castor oil was used in the cover, it improved the bioavailability of curcumin. Improved curcumin bioavailability increases the cellular proliferation rate and the rate of epidermal healing. What’s more, ricinoleic acid found in castor oil may have additional wound-healing properties due to its anti-inflammatory and analgesic properties.
• Immune system & liver function: A 1998 study assessed lymphocyte count in 36 healthy adults after a castor oil pack was applied to the abdomen. Total lymphocyte count increased to peak at 7 hours and decreased steadily by the 24-hour mark. However, lymphocyte count remained within normal limits after the decline. In another study,17 participants experiencing fatigue were given castor oil packs to apply to the abdomen region for 1.5 hours for 5 days per week over the course of 2 weeks. Mean total lymphocyte count decreased, and 2 study participants who started the study with high liver enzymes and cholesterol saw these values decline after 2 weeks. While these studies are old and preliminary at best, they still demonstrate the potential benefits of castor oil packs that require further investigation.
• Medical uses: In addition to its uses in medical devices, injectables, and microneedling for skin, castor oil is often used in transdermal drug delivery systems (TDDS). TDDS may be useful in the treatment of certain cancers as they can deliver medicines to the site of concern without systemic injury. Castor oil may also improve the bioavailability of the administered drugs.

Final Word

Castor oil has a history of a plethora of uses. More research is required to understand if it can be used as a therapeutic agent in human health, but preliminary research suggests that there are potential uses worth exploring further. As always, talk with your doctor, nutritionist, or another member of your healthcare team before using home remedies.