Ellen loved seafood and had eaten shrimp dishes frequently. This time it was different: her lips started tingling and then swelling, and soon she was finding it difficult to swallow or breathe. Fortunately, her friends acted quickly to get her to the emergency room where she discovered she was having an allergic reaction to the shrimp dip she had eaten.
Nearly everyone has some negative reaction to some foods on some occasions. The food may cause gas, cramping, an upset stomach or a headache. The rational response is to try to avoid that food at least in the quantity that brought on the reaction.
Allergies are generally much more serious and, as in Ellen’s case, can be life threatening. It’s important to know the difference between being allergic to a food and having a food intolerance or sensitivity.
A FOOD ALLERGY is an autoimmune reaction. The body’s immune system mistakenly identifies a protein or other substance in the food as an invader and over-reacts, producing antibodies to fight it.
The first time the food is eaten, the person notices no reaction, but the immune system produces imunoglobulin E (IgE) antibodies to fight it. The next time the food is encountered, these antibodies trigger the release of other chemicals such as histamine to attack what is perceived as an invader.
Histamine is a powerful chemical. In the skin, it produces hives or a rash; in the gastrointestinal tract, cramping, pain and diarrhea. The most severe reaction, often occurring within seconds, is anaphylaxis: constriction of the airways, a swollen throat, rapid pulse, lightheadedness and shock, with a dramatic drop in blood pressure. Without emergency medical attention, the person can die within minutes.
About 90 percent of allergies are to eight foods: peanuts, tree nuts, eggs, fish, shellfish, milk, soy products and wheat. Food manufacturers are required to report clearly on the label the possibility of even trace amounts of these foods.
An allergy typically develops early in life, but many children outgrow their allergies to milk, eggs, soy and wheat. Peanut, tree nut and seafood allergies are more likely to be lifelong. As in Ellen’s case, it’s also possible for an allergy to develop in adult life.
About six to eight percent of children and three to four percent of adults have some kind of food allergy. Exposure to even a small amount of the food can trigger a reaction, and there is no way to predict how severe symptoms will be. Some individuals have suffered severe allergic reactions simply by walking past a restaurant where shellfish is being prepared.
Since there is no cure, the only course is to avoid the food in any amount. A person with a food allergy must:
• be careful to read food labels,
• inquire about ingredients and food preparation when eating away from home, and
• carry epinephrine for use in emergencies.
For a child, of course, this strategy is difficult and requires the help of responsible adults.
A FOOD INTOLERANCE, by contrast, is a reaction of the digestive system. While symptoms (such as stomach pain, cramping and diarrhea) may be similar to those of an allergy, they usually come on more gradually and are rarely life threatening.
One of the most common, lactose intolerance, affects about 10 percent of Americans. It occurs because the person lacks the enzyme, lactase, needed to digest lactose, the main sugar in milk and most milk products.
Lacking the enzyme, the body uses bacteria in the intestine to break down lactose, and this process results in gas and the symptoms of bloating, abdominal pain and, in some cases, diarrhea.
There is a big difference, often misunderstood, between cow’s milk allergy and intolerance to cow’s milk, which is ordinarily due to lactose intolerance.
Persons with lactose intolerance can usually control their disorder by consuming smaller quantities of milk products or by taking lactase supplements. Persons with a milk allergy must avoid milk products, even in small amounts.
Another common food intolerance involves a negative reaction to additives such as monosodium glutamate, food colorings, preservatives or sulfites. Sulfites, which can also occur naturally in foods or generated as part of the winemaking process, can cause serious breathing problems in susceptible individuals.
Foods containing naturally occurring substances such as salicylates can trigger symptoms in some persons. Salicylates are found in many fruits, vegetables, nuts, coffee, beer and wine as well as in drugs such as aspirin.
Hereditary fructose intolerance occurs when a person lacks the enzyme necessary to break down fructose, a naturally occurring or man-made fruit sugar. Serious symptoms, including convulsions, jaundice and excessive sleepiness, can be seen soon after a child starts eating solid food or infant formula.
Celiac disease or gluten intolerance has some similarities to an allergy since it involves an immune system reaction. This is a unique reaction, however, that does not involve the production of IgE antibodies.
In susceptible persons, many of whom have a family history of the disorder, gluten causes an immune reaction that damages the lining of the small intestine, affecting its ability to absorb nutrients properly. A major ingredient of wheat, barley, rye and possibly oats, gluten is difficult to avoid, but that is what persons with this disorder must do.
In addition to abdominal pain, bloating and other symptoms, persons with celiac disease become malnourished and often have unexplained weight loss.
Both food allergies and food intolerances can be difficult to diagnose. Although a severe allergic reaction such as
Ellen’s is impossible to miss, the offending food may not be the main ingredient of the dish.
With a food intolerance, it can take 48 hours or longer for the symptoms to appear, and severity may vary according to how much of the offending food is consumed.
There is also a lot of misleading information circulating informally by word of mouth or the media. If you have questions about your reaction to certain foods, it’s best to talk to your doctor.
02/28/2012
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