Even when you’re aware of a food allergy, mistakes can happen. For example, ordering an Italian sub without confirming that it isn’t made with mortadella could lead to a reaction for someone with a pistachio allergy.

Food allergies occur when your body reacts to a food particle as if it were harmful. This kicks off an immune reaction that triggers the production of immunoglobulin E (IgE) antibodies and the release of histamines.

Sneezing, coughing, hives, itching, and facial swelling are common experiences in an allergic reaction. And for some people, a food allergy can lead to anaphylaxis, a serious and potentially life threatening medical condition.

Even if you’re extremely careful about your own or your child’s food allergy, there are sneaky ways these ingredients and foods can fly under your radar, and these mistakes are easy to make.

Food allergens can sneak into your diet through many foods, even in settings such as commercial sandwich shops.

Ordering an Italian-style sub sandwich might seem harmless, for example, but it could be made with a traditional Italian sausage called mortadella — which often contains pistachios. If you’re unfamiliar with traditional Italian cuisine, you might assume that a sausage would not contain nuts.

Ingredients such as curry pastes, fish sauces, and soup bases may contain dairy, nuts, soy, wheat, or other allergens.

Sauces and seasonings are another area where food allergy mistakes can happen.

Pesto sauce, for example, looks green and herbal but is traditionally made with pine nuts. Teriyaki and soy sauces frequently contain wheat. And if you have a fish allergy, be aware that Caesar salad dressings and Worcestershire sauce are often made with anchovies.

Lactose intolerance and a dairy allergy are not the same. If you have lactose intolerance, your digestive system has difficulty breaking down the milk sugar lactose. But if you have a dairy allergy, you experience an allergic reaction to milk protein.

Foods labeled “lactose-free” are not necessarily dairy-free. They may still contain milk or milk products. Even foods labeled “dairy-free” might have other milk-containing ingredients.

Commercially packaged foods can contain allergens in unexpected ways. For example, canned tuna can contain soy-based broth or may be manufactured with a milk-based binding agent.

Many commercially packaged beef products and sandwich meats are processed with milk. Milk powder or milk protein is often used as a binding agent in beef-based deli meats, and milk proteins are common in meat tenderizers.

It’s also possible for processed foods to be packaged in facilities that also package products containing milk, nuts, wheat, and other food allergens. Cross contamination with these allergens is possible in those environments.

The Food Allergy Safety, Treatment, Education, and Research (FASTER) Act identifies nine major food allergens that must be indicated on food labels in the United States:

  • milk
  • eggs
  • fish
  • crustacean shellfish
  • tree nuts
  • peanuts
  • wheat
  • soy
  • sesame

If you or your child has a food allergy to something not on this list, there’s a chance that food labels won’t include an allergy warning. A label might still list the ingredient — but it might not. The Food and Drug Administration (FDA) currently allows some ingredients to be listed collectively as “flavors,” “spices,” or “artificial flavoring.”

Even if you can drink alcohol without any allergy issues, trying a new cocktail or mocktail might not always be safe. Several mixed drinks, such as whiskey sours and gin fizzes, contain egg whites to help create the classic white foam on the top of the drink.

It makes sense that you would experience an allergic reaction after consuming an ingredient that you’re allergic to. But sometimes you might notice food allergy symptoms even when you haven’t directly ingested the allergen.

According to a research article from 2023, passive transfer of food allergens is possible through blood, saliva, semen, and breast milk.

If you or your child lives with a food allergy, being attentive to basic food ingredients isn’t always enough. Food allergens can hide in unexpected places such as sauces and product packaging, and even the most diligent people and parents can make mistakes.

When in doubt, leave it out. If you’re ever uncertain about a food or the ingredients it’s made with, opt for an alternative that you feel confident in.