"The FDA determined that four of the 52 products tested had potentially hazardous levels of milk allergen. These four products – all dark chocolate bars – were made by three different manufacturers. Together the four products were responsible for 12 positives out of the 119 samples....The agency found the 12 samples from the four products to have milk allergen levels ranging from 600 ppm to 3,100 ppm. The agency determined that, at these levels, the four products held the potential to cause severe reactions in consumers with milk allergy. The FDA took action as warranted to address each of these positives."
"The FDA does not define the terms “dairy free,” “milk free” or other “absence” claims, except for “gluten free.” Absence claims are voluntary statements that indicate a specific ingredient or food component is not present in a product. Absence claims, when used, must be truthful and not misleading, per the Federal Food, Drug and Cosmetic Act. If a product or references to a product on a company website were to bear a dairy-free or similar claim, the FDA would expect there to be no milk allergen in the product given that consumers with milk allergy depend on the accuracy of dairy-free claims for their health. The presence of milk allergen in a product bearing a dairy-free claim may lead the agency to conduct an investigation and to consider enforcement action, depending on the investigational findings."
https://www.fda.gov/food/sampling-protect-food-supply/fy1819-sample-collection-and-analysis-domestically-manufactured-dairy-free-dark-chocolate-products
FY18/19 Sample Collection and Analysis of Domestically Manufactured, Dairy-Free Dark Chocolate Products for Milk Allergen