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Castor oil is only medically recognized as a laxative; other alleged medical benefits, including treating cancer, lack scientific support

Posted on:  2024-03-20

Key takeaway

Castor oil is a plant oil with important applications in the manufacturing of soaps, lubricants, and coatings. Castor oil’s only recognized medical use is as a laxative to relieve constipation in the short term or to clear the bowels in preparation for medical imaging. But even its use as a laxative has diminished in the past decades, as castor oil has been eclipsed by newer laxatives with fewer side effects.

Reviewed content


“Scar tissue, bone spurs, tumors, [castor oil is] excellent for breaking that up”

Source: Facebook, TikTok, Barbara O'Neill, 2024-03-12

Verdict detail

Inadequate support: Castor oil is medically recognized only as a laxative for short-term relief of constipation. There is no evidence showing that castor oil is an effective cancer treatment. While researchers are evaluating other possible medicinal uses of castor oil, these haven’t been approved or scientifically demonstrated.

Full Claim

“Scar tissue, bone spurs, tumors, [castor oil is] excellent for breaking that up”


In March 2024, a Facebook video claimed that applying castor oil packs on the skin eliminates tumors, bone spurs, and uterine fibroids. The video originated on TikTok and was posted on the Facebook account of naturopath Barbara O’Neill, which has over 250,000 followers. This single post received more than 60,000 views.

Barbara O’Neill has been spreading health misinformation for years. In 2019, the Australian New South Wales Health Care Complaints Commission (HCCC) permanently prohibited her “from providing any health services […] whether in a paid or voluntary capacity”, including “health education services” in the country.

The ban followed an HCCC investigation that found that O’Neill’s health advice “discourages mainstream treatment for cancer, antibiotics and vaccinations”. The HCCC’s statement of decision published on 24 September 2019 noted that O’Neill was an unregistered practitioner with no recognized health-related accreditation. The committee concluded that O’Neill’s health advice posed “a risk to the health and safety of members of the public”.

Family physician Harriet Hall summarized the HCCC’s findings regarding O’Neill’s false and unsupported health claims in a Science-Based Medicine article.

However, the ban doesn’t prevent O’Neill from lecturing abroad. Videos of her lectures continue to receive millions of views on Facebook, TikTok, and YouTube.

Like many of her other health claims, O’Neill’s claims about the alleged benefits of castor oil are unsupported by scientific evidence. Regulatory agencies recognize castor oil’s only medical use as a laxative for relieving constipation or for clearing the intestines to facilitate tests like medical imaging. The evidence indicating its effectiveness for other uses is limited or nonexistent, as this review will show below.

What is castor oil?

Castor oil is a yellowish oil made from the seeds of the castor bean plant (Ricinus communis). Its main constituent is ricinoleic acid, a fatty acid with multiple industrial uses[1,2].

Castor bean seeds also contain ricin, a toxin that can be fatal even in small doses. But castor oil isn’t toxic to humans, as ricin remains in the waste left over after the oil is extracted by cold-pressing.

Castor oil is approved by the U.S. Food and Drug Administration and recognized by the European Medicines Agency (EMA) as a laxative for short-term relief of constipation. It works by stimulating the nerves in the gastrointestinal tract, which increases intestinal secretions and allows food to pass through the intestines more quickly.

Kevin Hopkins, a family medicine physician at Cleveland Clinic, explained that castor oil use has declined since more effective alternatives with fewer side effects became available. “Physicians haven’t really recommended castor oil for constipation for over 50 years,” Hopkins said.

Indeed, castor oil’s side effects include intense diarrhea, abdominal cramps, nausea, dizziness, and low blood pressure. Because severe diarrhea “can also lead to dangerous dehydration,” Hopkins said, castor oil “shouldn’t be consumed without a healthcare provider’s guidance—and it’s not something most providers are going to recommend”.

The Cleveland Clinic warns that consuming castor oil can worsen symptoms in people with appendicitis, inflammatory bowel disease, and gastrointestinal conditions in general.

Pregnant women should also avoid consuming castor oil, as it can cause premature contractions that may induce labor[3].

Castor oil doesn’t cure cancer

Castor oil has been used in folk medicine for centuries. The idea that it could treat cancer can be traced back to ancient Greek physicians Hippocrates and Galen, who hypothesized that breast cancer was due to an “excess of black bile” and recommended treating it with opium and castor oil[4]. Much later, in the 1920s, clairvoyant Edgar Cayce popularized castor oil packs again to eliminate tumors near the breast surface.

However, scientific evidence hasn’t shown that castor oil is effective at treating cancer. The U.K.-based charity Cancer Research UK states that there’s no reliable evidence that herbal remedies, like castor oil, can treat cancer in people.

One study published by Xie et al. in 1992 evaluated the effect of injecting extracts from castor oil into mice with cancerous tumors. Although the study is in Chinese, a 2007 report on the safety of castor oil by the American College of Toxicology discussed its results. According to the report, castor oil extracts suppressed tumor growth in roughly half of the mice and increased their life expectancy.

Another study published in Scientific Reports in 2019 showed that castor oil extracts inhibited tumor growth in breast cancer cells cultured in the laboratory and in mice with solid tumors[5].

However, these small, preliminary animal studies don’t provide sufficient evidence to conclude that castor oil is an effective cancer treatment in people.

First, cell and mouse models are very different from human beings, and the results from these studies don’t necessarily translate to humans. Second, the compounds used in these studies were purified extracts, not over-the-counter castor oil formulations. Finally, these extracts were injected into the animals rather than applied to the skin surface as O’Neill proposed.

Clinical studies evaluating the effect of castor oil on people with cancer are lacking. A 2005 case report showed that a mixture of balsam Peru, castor oil, and trypsin—a digestive enzyme that breaks down proteins—accelerated wound healing in a woman who underwent a total mastectomy for breast cancer. However, this study didn’t evaluate the effect of the mixture on the tumor itself.

It should be noted that castor oil is used as an ingredient in some chemotherapy treatments to improve the solubility of chemotherapy drugs. However, on its own, it doesn’t have any known anti-cancer properties in people, as several experts told Africa Check.

Speaking to Cancerwise, Gabriel Lopez, the director of the Integrative Medicine Center at MD Anderson Cancer Center, stated that castor oil “doesn’t have a role as a cancer treatment whether you take it by mouth or use it externally”.

Other proposed uses of castor oil have insufficient scientific support

Apart from touting castor oil as a cancer treatment, O’Neill’s video also promoted it as a cure for bone spurs and uterine fibroids. In a different Facebook video, O’Neill claimed that applying castor oil packs to the abdomen treats kidney and gallstones and irritable bowel disease.

Social media users have claimed that castor oil offers numerous health benefits, including helping with weight loss, removing toxins from the body, and improving vision. These claims are contradicted by a 2016 EMA assessment of castor oil’s medicinal properties. The EMA’s Committee on Herbal Medicinal Products found no evidence of any medical benefits beyond its use as a laxative. A 2023 reevaluation including new research data arrived at the same conclusion.

Therefore, none of the claims on social media are based on scientific evidence and some can be outright dangerous.

One of the many uses for which castor oil has been promoted is as an aid for losing weight. The U.S. National Eating Disorder Association explains that using laxatives for this purpose is not only ineffective but can result in potentially life-threatening health complications.

In 2009, a small trial suggested that consuming castor oil might relieve symptoms in people with knee osteoarthritis[6]. We couldn’t find any clinical study that evaluated the effect of castor oil on bone spurs, bony growths that form along bone edges and whose main cause is osteoarthritis. But according to the Mayo Clinic, the only treatment for bone spurs is analgesics to relieve the pain.

Very recently, in 2023, a TikTok trend prompted people to rub castor oil in the eye to prevent and treat vision problems[7]. Donny W. Suh, a pediatric ophthalmologist at UCI Health, told the digital medical publishing company MDLinx that these claims are unsubstantiated. “There is no scientific evidence to support claims made by TikTokers about [castor oil’s] benefits for vision including treatment of cataracts, glaucoma, floaters, presbyopia or other eye problems,” Suh said.

A few preliminary clinical trials reported that eye drops containing castor oil improved certain eye conditions like dry eye[8-10]. But using sterile eye drops with low concentrations of castor oil is very different from rubbing pure castor oil on the eyes. Many over-the-counter castor oils contain ingredients that can irritate the eye. Some can even be contaminated with microorganisms that may cause serious eye infections[7].

Another popular claim assures that consuming castor oil or applying it in packs to certain body parts helps remove toxins from the body. However, this claim has no scientific basis. A 2023 article in The Conversation explained that our liver, kidneys, lungs, and skin already have efficient mechanisms for removing waste products. Contrary to widespread claims, there is no evidence that the so-called “detox” products and practices help eliminate toxins, are necessary, or provide any health benefits.


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