The Diet Detective: Food allergies

The usual culprits of food allergies are considered peanuts, nuts, seeds, fish and shellfish.
Food allergies are serious business. In fact, according to Michael C. Young, M.D., assistant clinical professor of pediatrics at Harvard Medical School, approximately 11.4 million Americans (4 percent of the general population) have food allergies -- 90 percent of which are peanut and tree nut allergies. And food allergies lead to about 30,000 emergency room visits and 150 to 200 fatalities per year.

 

How do you know you have a food allergy?
It's tricky to identify an allergenic food after an isolated reaction. The usual culprits should be considered: peanuts, nuts, seeds, fish and shellfish. If more reactions occur, there is typically a pattern that makes the offending food easier to identify, says Anna Nowak-Wegrzyn, M.D., a professor specializing in pediatric allergy and immunology at the Mount Sinai School of Medicine. Diagnosis requires a combination of investigative work (trying to pin down the foods) and laboratory testing, such as skin prick tests and measuring antibody levels. "Frequently oral food challenges [feeding with the suspected food under physician supervision] are needed to conclusively establish the diagnosis," adds Nowak-Wegrzyn.

How do you know you're having an allergic reaction?
"Allergic reactions typically occur within minutes to no more than one to two hours after ingestion and contact with the food," says Young. The symptoms are as follows: Nearly all -- 90 percent -- produce skin reactions, about half -- 47 percent -- induce respiratory or multi-organ system responses, some -- 35 percent -- result in gastrointestinal symptoms, and about 20 percent result in anaphylaxis requiring epinephrine, he adds.

What's the difference between food intolerance and food allergies?
Allergic reactions are immunologic responses to food proteins that trigger the release of chemical mediators, such as histamines, which result in allergic symptoms: itching, rashes and hives, swelling, wheezing, vomiting, low blood pressure, anaphylaxis, etc. "Food intolerance results from the inability of the gastrointestinal tract to digest and metabolize components of the food," says Young. For example, in lactose intolerance, a deficiency of the enzyme lactase, which breaks down sugar in milk, results in GI symptoms, such as abdominal pain, bloating, nausea, vomiting, diarrhea or bloody stools.

What is happening biologically that creates a food allergy?
According to Young, "Genetically susceptible individuals are more prone to making immunoglobulin E (IgE) antibodies, which target specific food proteins. When the food proteins are ingested, these IgE antibodies bind to them and trigger the release of chemical mediators, such as histamine, from mast cells located in many tissues of the body, including the skin, lungs, circulatory system, digestive tract, mucous membranes of the nose, sinuses and throat." Histamine and other chemical mediators cause tissues to swell, itch and secrete mucus, airways to contract, blood vessels to dilate and blood pressure to drop, all effects of allergic reactions and, in the worst case, anaphylaxis.

What is anaphylaxis?
Anaphylaxis is an allergic reaction that can range from mild to life-threatening. It is most commonly seen as the effect of the rapid release of histamine, which, along with other released inflammatory signals, can cause hives/swellings (localized or all over the body), airway symptoms (throat itching or closure), cardiovascular symptoms (low blood pressure and dizziness), as well as gut symptoms (vomiting or cramping and diarrhea), says Jonathan Becker, M.D., a professor of medicine at the University of Washington and an allergy specialist. Anaphylaxis occurs in 40 to 50 percent of individuals with food allergies, adds Young.

What are the most common food allergies?
The eight most common (accounting for 90 percent of childhood allergies) are cow's milk, eggs, peanuts, soy, wheat, tree nuts, fish and shellfish. In children, allergies to milk, eggs and peanuts (in that order) are most common, whereas allergies to shellfish, peanuts and tree nuts are most common in adults, says Young.

Are some allergies worse than others?
Any food may cause fatal anaphylaxis, but peanuts and tree nuts have been identified as the most frequent causes of severe, life-threatening anaphylaxis, says Nowak-Wegrzyn.

How can you protect yourself if you do have food allergies?
There is no cure for food allergies, and the only way to prevent reactions is to avoid the offending food. Some must even avoid environmental exposures to the ingredients, such as nut oils or milk proteins in cosmetics, steaming of foods, etc.

Recently, the Food Allergen Labeling and Consumer Protection Act (FALCPA) was passed. It requires food manufacturers to list the major food allergens on ingredient labels. "Always read the label, even if you buy the product repeatedly, because the manufacturer may change the ingredients at any time. Pay attention to 'may contain' or 'processed in the same facility as,' especially if you have a history of reacting to trace amounts," advises Nowak-Wegrzyn.

How can you ensure your food is safe when you're eating out?
Preparation is critical. Contact the restaurant in advance, and make sure it's a food-allergy-friendly establishment. You need to be clear that this is not about being "picky," but about a life-threatening issue. When you arrive, talk to the manager and/or chef, and explain the nature of the allergy. "Inquire about how meals are being cooked. Ask them to pay particular attention to not sharing utensils, pots or pans that may be used for the allergenic food, and order only meals whose ingredients you can easily identify. Grilled meats are generally safer than meats in sauces," says Nowak-Wegrzyn.

Keep in mind that cross-contamination is very difficult to prevent, particularly in food preparation. Mixed use of deep fryers for seafood and non-seafood items, shared equipment, utensils, packaging and buffets with many different types of foods all create complications, says Young.

Can you develop food allergies later in life?
Yes, it is possible, especially with fish, shellfish, peanuts or tree nuts. It is extremely unlikely to develop an allergy to milk, eggs or wheat in adulthood, except in the setting of heavy occupational exposure such as in bakers, who are exposed to these food proteins in the air, says Nowak-Wegrzyn.

If your parents or other family members have food allergies how likely are you to get one?
Having one parent with allergies (of any kind) gives the child a risk of 33 percent; both parents having allergies (of any kind) gives the child a 66 percent risk. Specific allergies (e.g., wheat, pollen, cat) are generally not inherited, just the capacity to be allergic.

Can you really get an allergic reaction just by kissing someone who ate something you're allergic to?
According to Harvard's Young, this is a common type of allergic reaction. "If the kisser has eaten something, the residual food allergen remaining in the mouth, tongue and lips can cause a reaction in the allergic person receiving the kiss."

Is any one group of people more susceptible to food allergies than others?
Very young children (under age 3) who have signs of being allergic, such as eczema, asthma, nasal and sinus symptoms, and who have relatives with allergic problems are a highly susceptible group for developing food allergies, says Young.

Do food allergies arise, in part, from too-early introduction?
"The first two to three years of life is the window of time when the young child may be most susceptible to developing food allergies; hence the recommendation to avoid allergenic foods during this time period. Older children are less susceptible, as their immune systems are more developed," explains Young.

What are current recommendations for introducing common allergenic foods to children?
For genetically susceptible children at risk for developing allergies, the American Academy of Pediatrics recommends breastfeeding until 4 to 6 months of age (or feeding with a hypoallergenic formula), avoiding eggs until age 2, and avoiding peanuts, nuts and shellfish until after age 3 or older. "I recommend starting with rice cereal at age 6 months, then introducing green and orange vegetables and fruits, followed by the other grains -- oat, wheat, rye and barley. I would not start animal proteins until 1 year, beginning with chicken and turkey. Keep in mind, these recommendations are not evidence-based," says Young.

Are food allergies on the rise?
The prevalence of food allergies is increasing (demonstrating that food allergies are not just inherited); a recent study of peanut allergy prevalence shows a doubling of peanut allergy in children in the past five years. "The increase in food allergy parallels the increase in all allergic diseases in children, including asthma, environmental allergies and eczema. The Hygiene Hypothesis is a recent theory that explains this increase in allergic diseases with the observation that as younger populations have become healthier and more hygienic, with fewer infectious illnesses, their immune systems are finding other targets, such as allergens in the environment and diet," says Young.


Charles Stuart Platkin is a nutrition and public health advocate, author of the best seller Breaking the Pattern (Plume, 2005), Breaking the FAT Pattern (Plume, 2006) and Lighten Up (Penguin USA/Razorbill, 2006) and founder of Integrated Wellness Solutions. Sign up for The Diet Detective newsletter free at www.dietdetective.com.

Copyright 2006 by Charles Stuart Platkin

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