Allergy is a disorder of the immune system often also referred to as atopy. Allergic reactions occur to environmental substances known as allergens; these reactions are acquired, predictable and rapid. Strictly, allergy is one of four forms of hypersensitivity and is called type I (or immediate) hypersensitivity. It is characterized by excessive activation of certain white blood cells called mast cells and basophils by a type of antibody known as IgE, resulting in an extreme inflammatory response. Common allergic reactions include eczema, hives, hay fever, asthma, food allergies, and reactions to the venom of stinging insects such as wasps and bees.

Peanuts

Certainly many people have, know, or have heard about many people having allergies to peanuts. Including exclusively peanuts individuals can also develop allergic reactions to foods made with this product, and also foods related to peanuts such as peanut butter, beer nuts, peanut oil, and mixed nuts. People with allergies to peanuts should also stay away from other tree nuts because of cross contamination risks. It is well known occurrence that people with allergy to peanuts have or develop allergy to other types of tree nuts.

Hidden traces

Some sauces used in Mexican, Asian and African meals may contain peanuts in some form, Some types of candy, some chocolates, some natural and artificial flavors are also knows to include peanuts.

P.S. Always read labels on food products.

Eggs

Many people are allergic to eggs; however some people are far more sensitive that even cooking fumes can cause an allergic reaction.

Hidden traces

Some Ice creams, pastas, candies, hot dogs, mayonnaise, meatballs, breads, rolls and some baked goods, marshmallows, nougat and marzipan.

Milk

Milk is another food which many people are allergic too. Even very small amount of ingested milk can be enough to put someone in coma if they dont receive medical help on time. Other then Cows milk, goat milk, and sheeps milk, individuals can also be allergic to all types of other daily products such as, buttermilk, cream cheese, cream, butter, all types of cheese, half and half, yogurt, ice cream, pudding, sour cream.

Hidden traces

Some sources which contain milk in different forms is Veggie burgers, canned tuna, nondairy creamers, deli meats, chocolate, sorbet, hot dogs, salad dressings, breads, and mayonnaise.

Fish

People who are allergic to fish like tuna, catfish, salmon and others, should be aware of cross contamination risks of eating shellfish and other seafood.

Hidden traces

Many people dont know, but extremely important for people with allergies related to seafood to know that many Caesar salad dressing containing anchovy paste include fish. Also surimi, Worcestershire sauce, fish sauce, and caponata.

Tree Nuts

Many people have allergies to various types of tree nuts, such as cashews, pecans, hazelnuts, walnuts, Brazil nuts, pine nuts, almonds, chestnuts, macadamia nuts, pistachios and others. People with allergies to tree nuts should also avoid peanuts.

Hidden traces

People with allergies to tree nuts should always read labels of all processed foods. Take caution before eating types of candies, nougat, chocolates, cereals, marzipan, mortadella, pesto, and other natural and artificial flavors.

Shellfish

Shrimp, crab, lobster, crawfish, and more. Experts often caution those allergic to fish to be aware of cross-contamination risks of eating fish and other seafood.

Hidden traces

Fish stocks, flavorings (anything labeled "natural and/or artificial flavorings" may contain fish by-products).

Wheat

Wheat-based pastas, cereals, breads, bran; wheat germ, wheat berries, semolina (a type of wheat used to make pasta), kamut (used in cereals, crackers and pasta), bulgur, seitan.

Hidden traces

Ice creams, bouillon cubes, potato chips, deli meats, French fries, soy sauce, many processed snacks (too many to list), breadcrumbs, couscous, spelt, hot dogs.

Soy

Soymilk, tofu, tempeh, edamame, soybeans, soy protein isolate, soy sauce, soy nuts, TVP or textured vegetable protein (defatted soy flour), tamari, miso.

Hidden traces

Tuna, deli meats, hot dogs, vegetable broth, vegetable starch, textured vegetable protein, cereals, infant formulas, sauces, soups, many vegetarian products.