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Distinguishing a food allergy from a food intolerance

Ten minutes after eating shrimp scampi at a restaurant, Karen's lips swelled and she had difficulty breathing. Sandra, also seated at the table, had pasta carbonara and experienced bloating and abdominal cramping later that night. Both went to see the doctor, thinking they had developed a food allergy.

It is easy to confuse food allergy and food intolerance, but the two are vastly different and a food allergy could be life-threatening.

Many Americans think they have food allergies, but true food allergies are quite rare, occurring in less than 5 percent of the population. In the United States, fewer than 200 people die annually from food allergies.

Reactions to food allergies occur immediately, within two hours or less, while food intolerance reactions are delayed, sometimes occurring up to 72 hours after a particular food has been ingested.

In the case of a food allergy, a small amount — even traces — of food can trigger a reaction, and reactions occur every time the food is eaten. With food intolerance, reactions occur only when a lot of the food has been consumed or when that food is eaten frequently.

A food allergy can be life-threatening, causing anaphylaxis. Symptoms include generalized hives, tongue or throat swelling, difficulty breathing or swallowing, and a drop in blood pressure. Symptoms of food intolerance include gas, bloating, abdominal cramps, heartburn, headaches, low mood and eczema. Food allergy and food intolerance can both cause nausea, abdominal pain, diarrhea and vomiting.

Ninety percent of food allergies are caused by peanuts, tree nuts, fish, shellfish, milk, eggs, soy and wheat. The most common triggers for food intolerance include wheat, gluten, milk, fruits and vegetables.

If you have a food allergy, your immune system has developed a specific immunoglobulin to a specific food, and when you encounter that food, your body undergoes a predictable chemical reaction that leads to an allergic reaction. Having allergies, asthma or a family history of such things increases your risk of having a food allergy. Food intolerance can be caused by a number of factors, including the lack of an enzyme needed to digest a food. With lactose intolerance, for example, there is a lack of the enzyme lactose.

Two chronic conditions included in the category of food intolerance are irritable bowel syndrome and celiac disease. IBS causes cramping, constipation and diarrhea. Celiac disease involves the immune system and is triggered by eating gluten, a protein found in wheat and other grains. Food allergy to wheat is determined by an allergy skin-prick test, whereas celiac disease is diagnosed by a blood test or intestinal biopsy.

If you have symptoms after eating a food, an allergist can determine whether you have a food allergy or a food intolerance. It might be helpful to keep a log of what you have eaten, what symptoms occurred and when.

Because a food allergy can be life-threatening, avoiding the food is essential, as is carrying an EpiPen. If you have a food intolerance, it can be managed by limiting or avoiding certain foods or taking medication to help manage the symptoms.

Dr. Mona V. Mangat and Dr. Ami K. Degala are board-certified allergists and immunologists at Bay Area Allergy & Asthma in St. Petersburg.

Distinguishing a food allergy from a food intolerance 07/10/14 [Last modified: Thursday, July 10, 2014 6:13pm]
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