Symptoms of Food Intolerance.

What Are the Symptoms of Food Intolerance?
Symptoms of food intolerance include:

Nausea
Stomach pain
Gas, cramps, or bloating
Vomiting
Heartburn
Diarrhea
Headaches
Irritability or nervousness
How Common Are Food Allergies and Intolerances?
Food allergies affect about 2 to 4% of adults and 6 to 8% of children. Food intolerances are much more common. In fact, nearly everyone at one time has had an unpleasant reaction to something they ate. Some people have specific food intolerances. Lactose intolerance, the most common food intolerance, affects about 10% of Americans.

What Causes Food Allergies and Intolerances?
Food allergies arise from sensitivity to chemical compounds (proteins) in food. They develop after you are exposed to a food protein that your body thinks is harmful. The first time you eat the food containing the protein, your immune system responds by creating specific disease-fighting antibodies (called immunoglobulin E or IgE). When you eat the food again, it triggers the release of IgE antibodies and other chemicals, including histamine, in an effort to expel the protein "invader" from your body. Histamine is a powerful chemical that can affect the respiratory system, gastrointestinal tract, skin, or cardiovascular system.

As a result of this response, food allergy symptoms occur. The allergy symptoms you have depend on where in the body the histamine is released. If it is released in the ears, nose, and throat, you may have an itchy nose and mouth, or trouble breathing or swallowing. If histamine is released in the skin, you may develop hives or a rash. If histamine is released in the gastrointestinal tract, you likely will develop stomach pains, cramps, or diarrhea. Many people experience a combination of symptoms as the food is eaten and digested.