When Food Becomes The Enemy - food allergies and listing of allergens on food product labels

Imagine what it would be like if eating a peanut butter sandwich or some shrimp, or drinking a tall glass of milk left you vomiting, gasping for breath, and furiously scratching a fresh crop of hives. For some people with food allergies, that's reality.

A food allergy, or hypersensitivity, is an abnormal response to a food triggered by the immune system. While many people often have gas, bloating or another unpleasant reaction to something they eat, this is not an allergic response. Such a reaction is thought to not involve the immune system and is called "food intolerance."

Only about 1.5 percent of adults and up to 6 percent of children younger than 3 years in the United States--about 4 million people--have a true food allergy, according to researchers who have examined the prevalence of food allergies.

It's critical for people who have food allergies to identify them and to avoid foods that cause allergic reactions. Some foods can cause severe illness and, in some cases, a life-threatening allergic reaction (anaphylaxis) that can constrict airways in the lungs, severely lower blood pressure, and cause suffocation by the swelling of the tongue or throat.

An estimated 150 Americans die each year from severe allergic reactions to food, says Hugh A. Sampson, M.D., director of the Elliot and Roslyn Jaffe Food Allergy Institute at Mount Sinai School of Medicine in New York City and a food allergy expert.

The Food and Drug Administration's Center for Food Safety and Applied Nutrition has made it a high priority to boost consumer and food industry awareness of food allergens. As part of these efforts, the FDA is conducting food allergen education programs for consumers and industry. The agency also is developing a strategy for clear, easy-to-understand labeling of food allergens.

Allergic Reactions

Food normally doesn't provoke a response from the human immune system, the body's defense against microbes and other threats to health. In food allergies, two parts of the immune response are involved, according to researchers at the National Institute of Allergy and Infectious Diseases. One is the production of an antibody called immunoglobulin E (IgE) that circulates in the blood. The other part is a type of cell called a mast cell. Mast cells occur in all body tissues but especially in areas that are typical sites of allergic reactions, including the nose, throat, lungs, skin, and gastrointestinal tract.

People usually inherit the ability to form IgE against food. Those more likely to develop food allergies come from families in which allergies such as hay fever, asthma, or eczema are common.

A predisposed person must first be exposed to a specific food before IgE is formed. As this food is digested for the first time, tiny protein fragments prompt certain cells to produce specific IgE against that food. The IgE then attaches to the surface of mast cells. The next time the particular food is eaten, the protein interacts with the specific IgE on the mast cells and triggers the release of chemicals such as histamine that produce the symptoms of an allergic reaction.

If the mast cells release chemicals in the nose and throat, the allergic person may experience an itching tongue or mouth and may have trouble breathing or swallowing. If mast cells in the gastrointestinal tract are involved, the person may have diarrhea or abdominal pain. Skin mast cells can produce hives or intense itching.

The food protein fragments responsible for an allergic reaction are not broken down by cooking or by stomach acids or enzymes that digest food. These proteins can cross the gastrointestinal lining, travel through the bloodstream and cause allergic reactions throughout the body.

The timing and location of an allergic reaction to food is affected by digestion. For example, an allergic person may first experience a severe itching of the tongue or "tingling lips." Vomiting, cramps or diarrhea may follow. Later, as allergens enter the bloodstream and travel throughout the body, they can cause a drop in blood pressure, hives or eczema, or asthma when they reach the lungs. The onset of these symptoms may vary from a few minutes to an hour or two after the food is eaten.

Most Likely Suspects

Food allergy patterns in adults differ somewhat from those in children. The most common foods to cause allergies in adults are shrimp, lobster, crab, and other shellfish; peanuts (one of the chief foods responsible for severe anaphylaxis); walnuts and other tree nuts; fish; and eggs.

In children, eggs, milk, peanuts, soy and wheat are the main culprits. Children typically outgrow their allergies to milk, egg, soy and wheat, while allergies to peanuts, tree nuts, fish and shrimp usually are not outgrown.

Adults usually do not lose their allergies.

A Growing Problem

"The prevalence of food allergy is growing and probably will continue to grow along with all allergic diseases," says Robert A. Wood, M.D., director of the pediatric allergy clinic at Johns Hopkins Medical Institutions in Baltimore.

Wood says that research over the last three decades indicates that the number of people with allergies is skyrocketing in developed and developing countries, but not in underdeveloped areas.

"The fewer germs in terms of infection and the environment, the more time the immune system has to worry about things like allergens," says Wood. "Recent studies indicate that growing up in a large family or daycare center actually decreases the likelihood of developing an allergy."

Wood, who has had a severe peanut allergy since he was a toddler, says allergic reactions to foods can vary dramatically. "They can range from just a mild rash to very severe swelling in the throat and the airways in the lungs so that there is a complete inability to breathe," he says.

Wood's parents learned of their son's allergy when they introduced him to peanut butter. "The first time I had peanut butter I developed a rash and severe swelling in my face," he says. "I'm extremely allergic. Just being around when a peanut shell is broken and dust is being released is enough to cause a reaction.

"I've had a number of very dangerous reactions," Wood says. "People with a food allergy typically walk around with a little bit of fear all the time. Once it starts, it's a fear-generating experience."

Multiple Allergies

When Sarah Buster of Columbia, Md., was 4 months old, her parents discovered that an allergy to milk was causing her eczema, a chronic skin inflammation. Her skin improved with a switch to a soy-based formula. Sarah's doctor believed there was little cause for concern since many infants have eczema and most outgrow it by age 2. Sarah didn't. Tests later indicated that she was allergic to eggs, peanuts, tree nuts, penicillin, tree pollen, ragweed, dust mites, and dogs and cats.

It was then that Sarah's parents, Mike and Brenda Buster, began reading food labels as carefully as they would a legal contract. They joined a food allergy advocacy group, replaced the carpet in Sarah's bedroom and throughout the house with hardwood floors, placed dust mite covers over her bedding, gave away the family's dogs, and kept Sarah indoors as much as possible.

A small wooden chair with a wicker seat has taken the place of upholstered furniture for 9-year-old Sarah, and devices that filter dust, pollen and other particles hum both upstairs and downstairs.

For a time, soaking baths and ointment head-to-toe helped keep her skin moist, and a prescription antihistamine eased the itching enough so she could sleep. However, Sarah's eczema soon worsened again.

"Sarah's itching would be so severe that we could stand right by her and call her name and she would not respond because she was so focused on scratching," says Brenda Buster. "She would scratch until she bled because the pain felt better than the itch."

Finally, allergists at Johns Hopkins eliminated all conventional food and put her on a special formula made of amino acids. Sarah also started a four-month regime of prednisone, a drug that mimics the effects of the body's natural corticosteroid hormones and suppresses the activity of the immune system.

Eventually, her diet was expanded to six foods that doctors believed she was not allergic to: turkey, pork, rice, apples, grapes and tomatoes, supplemented by the special formula.

Sarah's skin cleared and after several months she began a series of dietary "challenges"--tests to determine whether specific foods cause an allergic reaction. Several years later, Sarah eats a more varied diet, and the Busters maintain a list of safe foods and those that cause an allergic reaction.

"The most difficult thing I have faced with my allergies is that when I see my friends eating something that I know I can't have, it just makes me feel left out," says Sarah.