Did you know that eating raw kidney beans can be toxic? According to the FDA, eating as few as 4-5 uncooked kidney beans can cause severe nausea, vomiting and diarrhea in 1-3 hours after ingestion. Uncooked kidney beans have an unusually high concentration of a chemical called phytohaemagglutinin that is destroyed when the beans are properly cooked by boiling. Apparently, cooking in a slow cooker may actually make the beans more dangerous because low temperature cooking increases the toxicity.
Other beans contain this chemical, but in much smaller amounts. The bottom line – be sure to cook kidney beans by boiling (after you soak them). DO NOT USE THEM AS TOYS OR ART OBJECTS FOR YOUNG CHILDREN. In addition to their toxicity, raw beans are a small object hazard for young children. If the child puts a bean into a body opening, the bean may get stuck, swell and become very difficult to remove.
REF: U.S. Food and Drug Administration, 5/2003