The privately held fast food chain said it was notified by one of its suppliers that it "had unintentionally added an undeclared dairy allergen in the recipe" for the lunch and dinner portions of its Grilled Chicken Filet and Grilled Nuggets.
Following the supplier's warning, the Atlanta-based company told FOX Business that it immediately notified guests of the issue.
Chick-fil-A updated its allergen and ingredient information on its mobile app and website. It also sent signage to all restaurants to warn guests of the mishap due to the fact that the affected products are still in the company's inventory.
However, Chick-fil-A said this is a temporary issue and that it's "actively working with the supplier" to ensure the allergen is removed and that this mistake does not happen again.
"We understand and take seriously the trust our guests place in us to make sure their food is how they expect it, and we apologize for this situation," Chick-fil-A continued. "Our priority is that our impacted guests can enjoy these products again soon."
The issue impacts all lunch and dinner portions of the Grilled Filets and Grilled Nuggets at all of its locations, but it does not impact its breakfast grilled filets.
In total, the restaurant chain that is closed on Sundays has 2,600 restaurants across 47 states, Washington, D.C., Canada and Puerto Rico.
Dairy is one of eight foods or food groups that account for the most serious allergic reactions in the country, according to the Centers for Disease Control and Prevention (CDC).
The symptoms and severity of these reactions can differ depending upon the individual. In some cases it can cause anaphylaxis, which is a "sudden and severe allergic reaction that may cause death," the CDC added.