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Food allergy or food intolerance?

Although many persons regularly experience untoward symptoms after eating certain foods, the underlying cause of their distress is more likely to be food intolerance than food allergy. Distinguishing between the two is important, not only because treatment of the problem is very different, but also because of the possible consequences of repeated exposure to the offending food.

Lactase deficiency is an example of food intolerance. Persons who produce too little of this enzyme have difficulty in digesting the milk sugar, lactose, with such resultant gastrointestinal disturbances as bloating, gas, abdominal cramps, or diarrhea after eating dairy products. Treating milk with a lactase supplement (e.g., Lactaid) or taking the supplement orally before eating dairy products may prevent the symptoms. (Not all persons who experience such disturbances after eating dairy products are actually lactase-deficient, however -- see sidebar, right.)

Other types of foods may produce gastrointestinal symptoms -- such as heartburn after eating spicy foods. Sometimes the cause is an underlying problem in the GI tract itself, such as ulcers, hiatus hernias, gallbladder disease, or inflammatory bowel disease. In many cases the cause of food intolerance is unknown, and avoiding the offending food is the only solution.

Food allergies are a more serious matter. For whatever reason, normally harmless protein substances in certain foods may be mistaken by the body's immune system for dangerous substances against which it must mount a defense -- the antigen-antibody reaction. The antibodies produced by an immune system gone awry then affect normal body cells, releasing histamine or other harmful chemicals that produce the allergy symptoms.

The most common of these allergic reactions are urticaria (hives) and itching -- either in the skin or in mucous membranes of the mouth, throat, lungs, or GI tract. The resultant swelling of the membranes produces such symptoms as tightness of the throat, breathing difficulty, asthma, vomiting, diarrhea -- and even loss of consciousness.

The severest allergic reaction is anaphylaxis, a sudden life-threatening fall in blood pressure, constriction of the airway, and swelling of the tongue and throat. Death may occur if the patient is not given an immediate injection of epinephrine to open the airway and constrict the dilated blood vessels -- the same treatment used for severe allergy to bee stings. Children and adults known to be susceptible to anaphylactic reactions to certain proteins should carry with them emergency epinephrine injectors, which can deliver an immediate dose of the drug, even through clothing.

It is thus important that food allergies be correctly diagnosed by an allergist so that the patient can avoid eating the offending food -- which may be difficult, given the widespread use of certain protein products in processed foods. Persons allergic to such proteins must read food labels with great care and not be embarrassed about inquiring of one's host or restaurant manager if unknown dishes contain shellfish or other foods to which one is allergic. The most common food allergies are those due to eggs, cow's milk, soy protein, shellfish, fish, legumes, wheat, and nuts (peanuts, walnuts, and cashews).

If You're Spending Extra Money for Reduced Lactose Milk, Try This Trick

Researchers at the Va Medical Center in Minneapolis found that one in three persons who thinks he is lactose intolerant is not. They also found that even many who are can stomach two cups of milk a day without suffering bloating, gas, cramps. or diarrhea, thereby eliminating the need for the more expensive reduced lactose milk. By spreading the two cups of milk between breakfast and dinner, the subjects had no more problem consuming regular milk than drinking milk treated with lactase.
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Author:Brown, Edwin W.
Publication:Medical Update
Date:Dec 1, 1997
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