This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
It has been said that in all cases where illness has followed the eating of ice cream, vanilla has been the flavor used, and is not occasioned by the copper utensils employed. However, the poisonous effects repeatedly observed have been referred by Schroff to the presence of cardol, resulting from the employment of the cashew-nut oil for improving the appearance of vanilla.
Manufacturers of carbonated beverages highly esteem vanilla as a flavoring material, which imparts a smoothness and delicacy to drinks, if used with judgment. For this purpose an adulterated article will not answer.