The FDA has upgraded a recall of Lay’s Potato Chips to the highest level possible, meaning consuming the chips will cause adverse health consequences. In December, Texas-based food manufacturer Frito Lay recalled a limited number of Lay’s Classic 13oz because the product could contain undeclared milk ingredients.

The Food and Drug Administration is using its most severe notice in a recall of more than 6,000 bags of chips in two states because of “undeclared milk.”

The FDA classified recalled Lay's Classic Potato Chips in two states under a Class 1 recall, meaning consumption could be fatal for people with a milk allergy.