Food allergies can cause severe reactions, so avoiding foods that cause them is critical. But it can be hard to know whether foods contain ingredients you're allergic to, especially when eating out. Knowing common hidden sources of food allergens can help.

The Food and Drug Administration (FDA) has identified eight major food allergens:

• Milk
• Eggs
• Peanuts
• Tree nuts (such as almonds, cashew, walnuts)
• Fish (such as bass, cod, flounder)
• Shellfish (such as crab, lobster, shrimp)
• Soy
• Wheat

Click on the tabs to the left corresponding to the major food allergens to see some possible sources of hidden food allergens. This is not a complete list; ingredients and food preparation and processing vary.

Hidden sources of milk and dairy products

• Deli slicers. These slicers often are used for both meats and cheeses.
• Tuna. Some brands of canned tuna contain casein, a milk protein.
• 'Nondairy' products. Some products claiming to be "nondairy" actually contain milk derivatives.
• Meat. Some meats contain a milk protein (casein) as a binding agent.
• Restaurant-prepared steak. Many restaurants add butter to their steaks after grilling, to enhance flavor.
• Certain medications. Some medications, such as Benadryl capsules, use a milk derivative (lactose) as a filler.

Hidden sources of eggs

• Specialty drinks. Eggs may be used to create the foam topping on specialty coffee drinks or in certain mixed drinks.
• Egg substitutes. Some brands of egg substitutes contain egg whites.
• Pasta. Some processed cooked pastas contain eggs or are processed on equipment also used to produce egg-containing pastas.
• Cosmetics, shampoos and medicines. These sometimes contain egg proteins or derivatives of egg proteins that could possibly trigger an allergic reaction — even if you aren't eating them.

Hidden sources of peanuts

• Artificial nuts. Some artificial nuts are peanut-based with flavoring added to make them taste like other nuts, such as walnuts or pecans. For example, mandelonas are peanuts soaked in almond flavoring.
• Arachis oil. This is another name for peanut oil.
• Chocolate candies. Many chocolate candies are produced on equipment also used for processing peanuts or peanut-containing foods. Cross-contact is common.
• Cultural foods. Many African, Chinese, Indonesian, Mexican, Thai and Vietnamese dishes often contain peanuts or are exposed to peanuts during restaurant preparation.
• Specialty baked goods and ice cream. Foods sold in bakeries and ice-cream shops often come in contact with peanuts.
• Sunflower seeds. Many brands of sunflower seeds are manufactured on equipment also used to produce peanuts.
• Nut butters. Many nut butters, such as cashew nut butter, are processed on the same equipment used to make peanut butter.
• Saliva. Allergy-causing proteins from peanuts and other food allergens can be passed through the saliva by kissing or sharing utensils, straws or cups with someone who has recently eaten peanuts — even after just brushing teeth or chewing gum.

Hidden sources of tree nuts

• Flavorings. Natural and artificial flavorings may contain tree nuts.
• Mortadella. This type of smoked sausage, made of pork, beef, wine and spices, may also contain pistachio nuts.
• Other foods. Tree nuts may be used in many foods, including barbecue sauce, cereals, crackers and ice cream.
• Household items. Some toys and beanbags may be filled with stuffing made from crushed nut shells.

Hidden sources of fish or shellfish

• Caponata. This Sicilian relish may contain anchovies.
• Caesar salad. Anchovies often are an ingredient in this type of salad.
• Meat sauces. Steak sauce or Worcestershire sauce may contain anchovies.
• Imitation crabmeat. Surimi (imitation crabmeat) contains fish.

Hidden sources of soy

• Peanut butter. Soy may be an ingredient found in peanut butter.
• Other food products. Soybeans and soy products often are used in baked goods, canned tuna, cereals, crackers, infant formulas, sauces and soups.

Hidden sources of wheat

• Imitation meat and seafood products. Wheat flour may be flavored and shaped to look like beef, pork or shrimp, especially in Asian dishes.
• Hot dogs. Wheat may be found as an ingredient in some brands of hot dogs.
• Ice cream. Wheat may be an ingredient in some brands of ice cream.
• Imitation crabmeat. Some types of surimi (imitation crabmeat) may contain wheat.
• Wreaths. Wheat products may be used to decorate wreaths and other home decor.