Food allergies are immune system reactions that occur shortly after consuming a specific food. Even a trace amount of the allergy-causing food can cause symptoms such as digestive issues, hives, or swollen airways. A food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis in some people.
A food allergy is easily confused with a much more common reaction known as food intolerance. Food intolerance, while annoying, is a less serious condition that does not involve the immune system.
Symptoms can range from mild to severe and affect each individual differently.

Not every person will experience all of the possible symptoms, and each reaction may be slightly different. However, common signs and symptoms include:

tingling in the mouth
burning sensation in the lips and mouth
facial swelling
a skin rash known as hives
wheezing
nausea or vomiting
diarrhea
a runny nose
streaming eyes

Common food allergy triggers[/i]
The most common allergenic foods account for about 90%Trusted Source of all food allergies, and people commonly refer to them as the “big eight allergens.” These foods are:

eggs
fish
milk
nuts from trees, including hazelnuts, walnuts, cashews, and pistachios
peanuts or groundnuts
shellfish, including shrimps, lobster, and crab
soybeans
wheat

What causes food allergies?[i]
In those with food allergies, the immune system treats a specific protein in a food as a harmful substance that may cause disease. It responds by producing antibodies that will play a role in attacking this protein.

When the person eats the same food again, the antibodies are ready, so the immune system reacts immediately by releasing histamine and other chemical substances into the bloodstream. These chemicals cause the symptoms of food allergies.

Histamine causes blood vessels to expand and the skin to become inflamed or swollen. It also affects the nerves, making the skin feel itchy. The nose may produce more mucus, resulting in itching, burning, and a streaming nose.

Treatments[i][/i]
The traditional way to manage food allergies has been to avoid the food that causes the reaction. People can also treat the symptoms of a reaction when they arise.

Oral immunotherapy is a relatively new and investigative way to manage food allergies. It involves giving the person increasing amounts of an allergen to increase the threshold that triggers a reaction.