Hidden Food Allergens: Where They Lurk

Hidden Milk and Egg Sources

Milk allergens appear in many unexpected products. Canned and deli tuna often contains casein as a protein binder. Some margarines, non-dairy creamers, and deli meats contain milk proteins. Hot dog buns frequently contain milk. Medications can use milk-derived lactose as an excipient. Some wines and beers are fined with milk-derived casein or egg albumin, though minimal residue typically remains.

Egg allergens appear in foam-topped cocktails (dried egg white), some pastas, egg-washed baked goods, breaded or battered foods, and many restaurant dishes where eggs are used as binders or coatings. Mayonnaise appears in unexpected places including some potato salads, coleslaw, tartar sauce, and creamy dressings that may not be labeled as 'mayo-based.'

Hidden Wheat and Gluten Sources

Wheat appears in many products beyond bread and pasta. Traditional soy sauce contains wheat (tamari is a wheat-free alternative). Many blue cheeses are ripened using bread molds. Malt (barley or wheat-derived) is used in cereals, flavoring agents, and vinegars. Meat products including some sausages, meatballs, and veggie burgers use wheat starch or gluten as a binder.

Caramel color made from wheat is used in cola beverages, soy sauces, and condiments. Hydrolyzed wheat protein appears in some cosmetics, shampoos, and skincare products — while skin absorption of protein is low, some wheat-allergic patients with skin barrier dysfunction react to topical wheat products. Modified food starch without a source declaration may be wheat-derived.

Hidden Peanut and Tree Nut Sources

Peanuts appear unexpectedly in many cuisines. African stews, mole sauces, and some chili recipes use peanuts or peanut butter as a thickener. Satay and pad thai sauces traditionally contain peanuts. Some vegetarian meat substitutes use peanut protein. Peanut oil — unlike highly refined peanut oil (which typically contains no detectable protein) — cold-pressed peanut oil retains allergen and should be avoided.

Tree nuts appear in pesto (pine nuts are often substituted with walnuts or cashews), many granolas and trail mixes, marzipan (almonds), nougat, Nutella (hazelnuts), some mortadella, and Indian sweets (burfi, ladoo). Pralines, brittle, and many European pastries and chocolates routinely contain tree nuts that may not be prominently labeled.

• Peanut: chili, mole, satay, African stews, some cereals, peanut oil (non-refined)
• Tree nuts: pesto, marzipan, nougat, Nutella, granola, pralines, baklava, some ice cream
• Milk: canned tuna, deli meats, non-dairy creamers, some wine and beer
• Wheat: soy sauce, malt vinegar, some blue cheese, meat products, caramel color
• Egg: pasta, wine (fined with egg), cocktail foam, mayonnaise-based products
• Sesame: tahini, hummus, sesame oil, breadsticks, Asian marinades, some breads

Non-Food Sources of Food Allergens

Food allergens can appear in non-food products that may affect highly sensitive individuals. Milk and egg proteins are used in some cosmetics, hair products, and body lotions. Wheat protein (hydrolyzed wheat) appears in some shampoos, conditioners, and topical creams. Peanut oil is used in some cosmetics and massage oils — while typically refined, sensitive individuals may react.

Medications can contain allergens as inactive ingredients (excipients). Some vaccines contain egg protein (influenza vaccine, yellow fever vaccine). Certain medications are manufactured in facilities that process nuts. Patients with severe food allergies should inform their pharmacist of all allergens so excipient ingredients can be verified, particularly for compounded medications.