Allergies to cow’s milk are the most common food allergy, affecting roughly 2.5% and 0.3% of adults in the US. Casein is the major protein in milk (80% of total milk proteins) and constitutes a major allergen of clinical importance. Because it is present at high levels in milk, casein is a useful indicator of the presence of milk residue. Casein is used widely in the food industry, along with other derivatives and isolates from milk, and can be found in such unexpected items such as processed meats, non-dairy creamers, canned fish and wines.  Companies producing non-dairy products should ensure their raw and finished products have not been contaminated with milk protein during manufacture, to prevent possible allergic responses in sensitized individuals.