AbstractCastor bean meal contains an extremely potent allergen and a highly toxic protein, ricin.Accidental ingestion of castor beans has caused deaths of farm animals, and exposure to dust from oil mills which process castor beans has caused outbreaks of allergy in the neighbourhood.Evidence from feeding trials suggests that heated castor meal is not toxic and the use of detoxicated meal as a source of protein in animal feed has been proposed. The allergen is more stable to heat than is ricin and might therefore constitute a hazard to man if the meal were to be used for this purpose; at present it is used as a fertiliser. However, it has been found that heating the meal in steam at 15 p.s.i. not only detoxicates the meal but also inactivates the allergen.