Herb library · Herb · Ricinus communis
Castor oil
The oil pressed or boiled from castor seeds, a household purge in Caribbean homes for generations and still sold as a laxative. It empties the bowels strongly; trials of it for starting labor are small and poor. The seeds themselves are poisonous.
Serious warning
The castor seeds (not the oil sold as a laxative) contain ricin, a highly toxic protein. A hospital series from Iran (Avicenna J Phytomed, 2026) describes repeated vomiting in 11 of 12 people after swallowing one to ten seeds.
Traditional use
In 1756 Browne described people across the Caribbean sugar colonies pounding castor seeds and boiling them until the oil rose to be skimmed off, and using it as a purge and as lamp oil. In British Guiana, castor seeds grown in the colony were shown at the 1885 exhibition beside Creole and Amerindian bush medicines. It is still taken as a strong laxative, and, as the Cochrane review notes, it has been widely used in midwifery to try to bring on labor.
What studies show
- Limited
Bowel cleansing: castor oil has been tested in several trials as a bowel preparation before colonoscopy and X-ray exams. In one randomized trial of 70 people, a magnesium citrate and bisacodyl regimen cleaned the bowel better than 60 mL of castor oil, and castor oil caused more stomach pain and was harder to accept.
- Limited
Starting labor: a Cochrane review found three small trials (233 women) of single doses, of poor methodological quality, too small to show anything but large differences. Every woman who took castor oil felt nauseous.
Be careful of
Cautions
- PregnancyDo not take castor oil in pregnancy to bring on labor except under your midwife's or doctor's care. The Cochrane review found no clear benefit and nausea in everyone who took it.
- AmountIt is a strong laxative: expect cramping and loose stools. Doses in the trials were a single 60 mL dose for bowel cleansing.
- NoteNever eat castor seeds or use homemade oil pressed raw from them. The seeds contain ricin; in a hospital series from Iran, people who swallowed one to ten seeds vomited repeatedly and needed hospital care.
- ConditionBelly pain that could be appendicitis or a blockage, or constipation that lasts, needs a clinician, not a laxative.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“This luxuriant plant is frequent in all the sugar-colonies, and cultivated by many people for the sake of its oil; which is commonly obtained by pounding the seeds or kernels freed from the husks, and boiling them in water until all the oily particles rise to the top”
“Castor oil seeds were well shown, but all the samples from this colony were of the small variety. If this plant should ever be cultivated for oil an importation of the large seeds would be necessary.”
Sources
- Castor oil, bath and/or enema for cervical priming and induction of labour (Cochrane Database Syst Rev, 2013) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
- Magnesium citrate-bisacodyl regimen proves better than castor oil for colonoscopic preparation (J Gastroenterol Hepatol, 1999) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
- Clinical and laboratory findings in patients with castor bean (Ricinus communis L.) poisoning (Avicenna J Phytomed, 2026) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
Reviewed September 25, 2026.