"Natural flavor (also known as "natural flavoring") is a catch-all term used on food labels. Many potential food allergens can hide in natural flavor.
According to FDA food label regulations, natural flavor or flavoring may be from:
The Food Allergen Labeling and Consumer Protection Act (FALCPA) is helpful to some extent. FALCPA requires food manufacturers to list if one or more of the 8 major food allergens are in a natural flavor. This includes: milk, egg, peanuts, tree nuts, wheat, soy, fish and crustacean shellfish.
If natural flavor contains one of the 8 major allergens, you will see the name of the major allergen within the list of ingredients. For example, the label may say “natural flavoring (soy)” or it may say “Contains: soy” at the end of the ingredients list.
But, you will need to be careful about natural flavor if you are managing food allergies other than the top 8 major food allergens. Manufacturers do not have to state if other allergens like mustard or sesame are in a natural flavor. If a food has natural flavors, check with the manufacturer to be sure that food is safe for your food allergies.
Food and Drug Administration. (2004). Foods; labeling of spices, flavorings, colorings and chemical preservatives. In Food Labeling. (21CFR101.22). Washington, DC: U.S. Government Printing Office via GPO Access. Retrieved March 21, 2015 from http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.22