Q: Recently, I went to my doctor complaining of an itchy throat after eating. He told me that I have a food intoler ance. What is the difference between a food intolerance and a food allergy?

	Bill Wade, Post-Gazette Crustacean shellfish, such as shrimp, are among common allergens. Others are milk, eggs, peanuts, soybeans, wheat and fish. Click photo for larger image.

A: The good news is that the doctor told you that you have a food intolerance and not a true food allergy. The difference deals with whether the immune system is or is not involved. Because a food allergy involves the immune system, it is typically more severe than a food intolerance.

Unfortunately, there is much confusion as a result of the hype caused by access to misinformation, which can be very dangerous. Here's what you need to know about food sensitivities, intolerances and allergies.

Food sensitivities: There are two types of food sensitivities -- food intolerances and food allergies. Since a food allergy does involve the immune system, it can be life threatening. Your doctor correctly diagnosed your itchy throat in response to a food as a food intolerance since it does not involve the immune system.

Food intolerance: These are the most common type of food sensitivities. They are generally less severe, shorter-lived, and more localized. There are actually two sub-types of intolerances -- metabolic food disorder and food idiosyncrasy.

A metabolic food disorder is the type that occurs when a person is genetically unable to digest a component of food. An example of this would be lactose intolerance or the inability to digest lactose (milk sugar).

A food idiosyncrasy is an abnormal response to a food with an unknown reason as to why it happens. The symptoms can be similar to an allergy and can be mild to severe. Sulfites used to preserve certain foods and drinks, like wine, are an example of a food idiosyncrasy and can result in a sulfite-induced asthma attack.

Food allergy: While this is not as common as food intolerances, it can be severe and potentially fatal. A true food allergy occurs when a person consumes a specific protein component of food. The body mistakes the protein as a threat and produces an antibody to fight against it.

With repeated intake of the offending food, the body releases histamine and other biochemicals to fight off the allergen, thus producing the typical symptoms of an allergy attack. These symptoms can include hives, a sensation of warmth, asthma symptoms, swelling of the mouth and throat area, difficulty breathing, vomiting, diarrhea, cramping, a drop in blood pressure and loss of consciousness. These symptoms may begin in as little as five to 15 minutes or as much as two hours after exposure to the allergen, but life-threatening reactions may progress over hours.

According to the Food and Drug Administration, food allergies affect about 2 percent of adults and 5 percent of infants and young children. Most common food allergies come from eight major foods -- milk, eggs, peanuts, tree nuts, soybeans, wheat, crustacean shellfish and fish.

Anaphylactic shock is a rare, potentially fatal, response to a protein in one of these foods.

At this time there is no cure for food allergies, and the only method of preventing a reaction is avoiding the allergy-causing food. To make it easier for consumers to identify foods that contain major allergens, the Food Allergen Labeling and Consumer Protection Act (FALCPA) became effective on Jan. 1, 2006. The law requires all food labels to declare in plain English the presence of any of the top eight allergens.

Some foods, however, are exempt from the FALCPA requirements. These include meat, poultry, fruits, vegetables and alcoholic beverages. Therefore, if you know you have a food allergy to one of the top eight offending foods you must carefully read the ingredients on labels to determine their presence.

From your description it appears that you did suffer from a food intolerance as your doctor stated. However, you may never know the exact cause of this reaction.

If you have noticed that you routinely experience adverse symptoms after eating certain foods, the first thing you may want to do is keep a log of your experiences. Second, make an appointment with your physician and take the food log to your appointment.

For more information on food allergies, check out www.foodallergy.org/ and www.cfsan.fda.gov/ (search food allergy) or call your local Penn State Cooperative Extension office.