Is castor oil dangerous?

Is ingesting castor oil toxic?

The castor oil, extracted from the seeds of the plant Ricinus communis, has been known since antiquity for its multiple uses. Today, it is found in many applications: formulation of personal care products, lubricants, plasticizers, or as a laxative. However, despite this wide use, it raises concerns because ricin is present in the seeds. Ricin is a glycoprotein toxin that can cause severe gastrointestinal symptoms, such as severe abdominal pain, vomiting, or diarrhea, and lead to severe dehydration. Mortality remains low if symptoms receive prompt medical care.

To date, the literature reports approximately fifty cases of ricin poisoning worldwide (PubMed, ScienceDirect, and Google Scholar, 1980–2020).

However, it is important to note that ricin is found primarily in raw castor seeds and is normally absent, or present only in trace amounts, in the oil. When castor oil is extracted, processes such as cold pressing eliminate this toxin to a negligible level. A recent study reported about 35 ± 13 µg/L of ricin in cold-pressed castor oil. An oral toxic dose is estimated at 1 to 5 µg per kilogram of body weight. Thus, ingesting about 30 mL of castor oil, a common laxative dose, delivers approximately 1 µg of ricin. This remains well below the toxic threshold.

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What are the side effects of castor oil when applied topically?

The castor oil is generally well tolerated when applied to the skin.

However, like any ingredient, it is not entirely free of irritation or allergic reaction risks. In rare cases, castor oil has been linked to contact dermatitis. One case report describes a 30-year-old woman who experienced lip darkening for one year accompanied by itching and swelling. After a clinical investigation and a series of patch tests, a pigmented contact dermatitis induced by ricinoleic acid was detected. The reaction was due to castor oil in her lipstick. After she stopped using it, her lips nearly returned to their original color.

Note : This type of reaction to castor oil is rare. In most cases, castor oil or products containing it are not associated with adverse effects. As a precaution, it is best to perform a test the first time you use castor oil or a new skincare product. Apply a small amount inside your elbow and wait 24 to 48 hours to check for a reaction. This habit prevents widespread reactions.

The use of castor oil on lashes or brows to strengthen or boost growth is popular. Some wonder if it's dangerous for the eyes. To date, no scientific source reports castor oil toxicity for the eyes. Studies have examined its effects in managing blepharitis, an eyelid inflammation. Applying castor oil to the lash line can reduce inflammation and relieve eye dryness. Use small amounts and a clean, disinfected spoolie.

Are there side effects associated with applying castor oil to hair?

It is worth noting that castor oil is linked to two opposing misconceptions: some believe it can stimulate hair growth, while others believe the castor oil might cause hair loss. To date, no scientific study has shown that castor oil promotes hair shedding. Several studies suggest that ricinoleic acid may inhibit prostaglandin D2 (PGD2) activity. This protein, in synergy with its metabolite 15-dPGJ2, halts hair growth by binding to the molecular receptor GPR44. Castor oil could prevent hair loss.

However, scientific literature has described a very rare adverse effect associated with castor oil: the acute hair felting, referring to a tight, disorderly entanglement of hair fibers that makes detangling impossible. A 20-year-old woman, after applying castor oil mixed with coconut oil to her hair for the first time, experienced sudden, severe matting. After washing and attempting to dry her hair, strands twisted and compacted into a solid mass resembling a bird’s nest. Detangling attempts worsened the matting and caused pain. The only solution was to cut off the matted hair.

Acute hair matting following application of a castor and coconut oil blend.
Source: KIRUTHIKA S. et al. Castor oil—the culprit of acute hair felting. International Journal of Trichology (2017).

Even though it may sound alarming, acute hair matting is a rare phenomenon : only 17 cases have been reported worldwide, from all causes combined. In most cases, castor oil poses no risk to hair. We recommend using it sparingly. A few drops suffice to provide its benefits. Rinse hair afterward to avoid weighing it down.

Can castor oil be used safely during pregnancy?

Taken orally, castor oil has long been used to induce labor in pregnant individuals. After ingestion, castor oil’s ricinoleic acid is released by intestinal lipases. It exerts a potent laxative effect and promotes uterine contractions by interacting with prostanoid EP3 receptors on intestinal and uterine smooth muscle cells. In mice, deleting these receptors abolishes both the laxative effects and the contractions induced by castor oil, confirming their key role. Pregnant individuals sometimes avoid castor oil, fearing it may increase the risk of miscarriage.

Some studies highlight potential risks. A 39-year-old patient at 39 weeks of gestation ingested 5 mL of castor oil to induce labor. She experienced intense uterine contractions, membrane rupture, and required an emergency cesarean section because her cervix remained closed. During surgery, a 2 cm uterine rupture was discovered and required immediate surgical repair. This case underscores the need for caution with self-medication.

In a controlled medical setting, administering castor oil may induce labor at term. A blind study with 200 pregnant women showed that a 60 mL dose of castor oil between the 40th and 41st week of pregnancy significantly reduced the risk of prolonged pregnancy : only 17.1% of women in the intervention group went past term, compared with 41.5% in the control group. No maternal or neonatal complications were reported. These results were obtained under close medical supervision.

These effects of castor oil concern only its oral absorption. When applied to skin or hair, it remains on the surface without systemic uptake. Topical use of castor oil is possible during pregnancy.