There's a cold pressing and filtering process that removes the toxic protein. Probably not something readily done at home, and the consequences of doing it wrong are not something you'd want to risk.

I think you'd also have to harvest a lot of castor beans to make enough oil for it to be worthwhile, and apparently handling lots of beans is risky in itself.

"Allergenic compounds found on the plant surface can cause permanent nerve damage, making the harvest of castor beans a human health risk. India, Brazil and China are the major crop producers and the workers suffer harmful side effects from working with these plants."

Castor oil actually is toxic when taken internally - it not only increases loosens the stools, it also damages lining of the intestines. Dosing animals with castor oil is an experimental model for inducing colitis.

Haitian women use the castor bean oil externally on their hair & for preventing stretch marks of pregnancy. The freshly mashed leaf is used as a warm poultice when milk secretion is a problem (infant is not fed it).
Castor oil extraction is a cottage industry, labor intensive & the oil sells at a premium in Haiti, to women.

"The freshly mashed leaf is used as a warm poultice when milk secretion is a problem (infant is not fed it)."

Since castor oil is readily absorbed into the skin, and freshly mashed leaves are not purified of the toxic protein, this treatment sounds like a bad idea even if one is not nursing an infant.

Hi eric,
Sounds risky - not sure how they select/place the leaf.

Had a chance to see the following Castor use out side of Haiti. If had the patience probably there are more cultures that routinely use(d) the plant.
(1) Duke Ethno-botanical Dictionary:
in Columbia leaf poultice on top of "corozo" oil used to treat stomach inflammation
(2) botanical.com:
in Canary Island fresh leaves used externally to increase milk flow
(3) innvista.com:
in Mexico leaf poultice for chest, cough, fever, bruises, boils, neuralgia, abscesses
(4) flowersofindia.net:
in India warmed & crushed leaf poultice for bleeding piles, sores, gout, rheumatic swelling; and for lactation (apparently warmed, but not crushed)
(5) ethnoveterinary remedies:
in Trinidad young leaf passed rapidly over flame wrapped around clay on injured tendon; sometimes roll bottle over leaf first
(6) www.botanical.com/site/column_poudia/172_andi.html
Ayurveda Medicine & also Unnani systems' very extensive traditional uses are discussed

Please pardon my error; here's the correction - I meant to transcribe "poudhia" , with an "h".
So the # (6) link I posted about Castor Bean, called Andi in India, is:
www.botanical.com/site/column_poudhia/172_andi.html

The Castor Bean seeds' toxic compound Ricin, not being water soluble, is not in Castor Oil; unless due to production cross contamination.
From USA National Institute of Health (1992) (= NIH pub 92-3131) regarding castor oil:
* human toxicity = 1-2 pints orally of undiluted castor oil
* human hyper-sensitivity possible = angiodema, asthma, rhinitis & scalatiniform rash in oil production workers
* 10% castor oil dietary component fed experimental rats conclusion = no toxicity to any specific organ, organ systems or tissue; ie: no histo-pathological lesions & no hepato-toxicity from Castor oil
* Ricinoleic acid is +/- 87% of Castor bean oil = a fatty acid liberated in small intestine by lipase enzyme & it is poorly metabolized, so residues linger in G-I tract
* effects of Ricinoleic acid = inhibition of water & electrolyte absorption, stimulates water secretion into large intestine lumen & depresses small intestine contractions