Ricin is highly toxic, but castor oil is refined, so it is safe to consume. Although refined castor oil is edible.

But castor seeds are deadly; a single castor seed can poison a horse, and its toxicity comes from ricin, a substance so poisonous that workers who collect castor seeds must follow strict specifications to avoid accidental death. Nonetheless, many workers who collect castor seeds are still inadvertently poisoned.

Expanded Information:

< p>Castor beans have high oil content, because the oil is used for different purposes, so the method of oil extraction is different, medicinal castor oil is cold pressed with a hydraulic press at a temperature of not more than 50, otherwise some of the impurities will be dissolved in the oil and can not be used for medicinal purposes.

The oil obtained by cold pressing is called No. 1 castor oil. The cake is crushed and pressed again or leached to produce No. 3 castor oil (no No. 2) for industrial use. Castor oil obtained by direct pressing with screw press or pre-pressing - leaching can only be used as industrial oil. Castor oil is a pale yellow viscous non-drying oil, soluble in most organic solvents other than fatty acid hydrocarbons, especially with the characteristics of alcohol show solubility.

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Baidu Encyclopedia - castor oil