Overreaction

Scott H. Sicherer, a pediatrician specializing in allergies and immunology at the Icahn School of Medicine at Mount Sinai, takes the idea of ​​early desensitization one step further. He suggests that the best way to avoid allergies is to expose children to a wide variety of foods at a young age, run in the open air and "play in the dirt." A little less protection from the world, he says, is the best defense against allergies.

The article is published with the approval of Scientific American Israel and the Ort Israel network

A few years ago, a 15-month-old baby girl was rushed to the emergency room at Southwestern University Medical Center in Dallas, Texas. The girl's stomach, arms and legs were swollen and her palms and feet were covered with moist yellow scales. Laboratory tests revealed many nutritional problems.

During the year preceding her hospitalization, the mother complained to the doctors that routine milk substitutes cause her baby to vomit and have rashes. The mother and the pediatrician assumed that the girl was allergic to the particular milk substitute she had been eating until then and switched to feeding her with goat's milk. But the symptoms continued. This time the doctor ordered to switch to a diet of coconut milk and rice syrup. At the age of 13 months, the pediatrician again noticed a red rash and swelling and ordered a first allergy test. In the test, a high sensitivity to coconut was found and coconut milk was removed from the menu. But with the reduction of the menu to rice milk only, the girl's symptoms worsened.

In the emergency room, the doctors determined that the girl was suffering from a rare nutritional disorder in developing countries called kwashirkor. They fed her intravenously, and a team of doctors, which included pediatric allergy specialist J. Andrew Bird, tested her sensitivity to coconut milk and cow's milk, wheat, soy, egg white, fish, shrimp, green beans and potatoes using complex methods. To the mother's astonishment, the toddler was not found to be sensitive to any ingredient. After a few days of a regular diet and antibiotic treatment to disinfect her skin from various infections, the girl was released from the hospital without dietary restrictions. (Her indigestion seems to have been caused by a variety of common ailments that would have gone away anyway.)

The problem was not with the baby but with the tests. The conventional allergy tests, in which the skin is scratched with a needle coated with protein taken from a suspect food, provoke signs of irritation in 50% to 60% of the cases even when the patient is not actually allergic to the food. "When you start with the wrong test, as was the case here, you end up with a false positive," says Byrd, who co-authored the article describing the Dallas case in 2013 in the pediatrics journal Pediatrics. False positives also cause many people to avoid foods that do not cause them any harm. Byrd said he and a team of researchers found that 112 of the 126 children diagnosed with multiple food allergies were not actually allergic to at least one of the foods that doctors had warned could be life-threatening.

Keri Nadeau, director of the Shawn N. Parker Center for Allergy Research at Stanford University, says many pediatricians and family physicians are unaware of these testing flaws. "When it comes to diagnosis, we've been treading the same ground for 20 years," she says. To move forward, Nadeau and other researchers are developing more advanced and user-friendly methods.
Food allergies are a real phenomenon that can be fatal, but also a wrong allergy diagnosis can cause serious problems for the patient. First, the misdiagnosis does not solve his real problems. Second, the cost of misdiagnosing allergies is high: a few years ago, Ruchi S. Gupta, a pediatric allergist affiliated with the Feinberg School of Medicine at Northwestern University, estimated the annual cost of food allergies in the United States, and found that it reaches About $25 billion, or $4,184 per child. Some of the amount is the cost of medical treatment, but most of it is due to the decrease in the work productivity of the parents.

And it also has a mental cost: children who believe they are allergic to food tend to report higher levels of stress and anxiety, as do their parents. Every sleepover, picnic or flight involves the worry that the boy or girl will be one peanut away from an emergency room visit or worse. Parents and children must always have medication and a syringe to stop an acute allergic reaction. The fear of a lifetime of such vigilance may weigh heavily on the parents. Some of them have gone so far as to purchase dogs trained to smell peanuts, or have switched to homeschooling to protect their children from exposure to the harmful food and from attaching the negative social label that the allergy brings.

John Lee, a pediatric allergist and director of the Food Allergy Program at Boston Children's Hospital, has heard too many horror stories. "Food allergies can cause terrible isolation for a child," he says. "One parent told me that their son was forced to sit alone on a platform during meals. Brothers and sisters of allergic children may develop anger because in many cases their parents give up family vacations and eating in restaurants because of fear of the results."

Diagnosis of food allergy usually begins with the patient's medical history and a skin scratch test. If the scratch does not cause swelling surrounded by itchy redness, it is almost certain that the subject is not allergic to the substance. On the other hand, it is more difficult to interpret positive results because skin irritation does not necessarily indicate a true allergy, which is a hypersensitivity of the immune system that spreads throughout the body. In a true allergy, components of the immune system in the blood such as IgE antibodies are activated as a result of exposure to the substance that causes the allergy - the allergen. The antibody binds to cells in the immune system called mast cells (or mast cells). These cells trigger the release of a chain of chemicals that cause various types of inflammation and irritation. However, the level of antibodies unique to a certain allergen in the blood is quite low, even in allergic people, so a simple blood test is not effective.

The "gold standard" of food allergy diagnosis is a placebo-controlled test. The patient receives a food suspected of causing an allergy and the doctors compare his body's reaction (skin rash or swelling, for example) to the one obtained after eating food of a similar appearance that is not suspected of causing an allergy. For example, a patient who is suspected of being allergic to eggs will receive a cake that contains a small amount of eggs and a cake that does not contain eggs at all. In an optimal test, neither the patient nor the examiner know which cake contains eggs. According to Lee, the accuracy rate of these tests is 95%, both for a positive and negative answer.

The table of the most common food allergies in children. Credit: The Prevalence, Severity, And Distribution of Childhood Food Allergy in the United State by Ruchi S. Gupta and colleagues, Pediatrics. Published online on June 20, 2011.
The most common food allergies in children (based on self-reports of symptoms). Credit: The Prevalence, Severity, And Distribution of Childhood Food Allergy in the United State by Ruchi S. Gupta and colleagues, Pediatrics. Published online on June 20, 2011.
Unfortunately, the process is complex, expensive and not widely used. Experts agree that only a few receive such a test. James Baker, a physician, immunologist and CEO of the Association for Food Allergy Education and Research (FARE), says his organization is establishing 40 centers across the US to deal with the problems such tests pose while taking the necessary precautions. "We have to be ready to provide treatment on the spot or transfer to the emergency room if there is an allergic reaction," he says.

Scientists are also looking for tests that are easier to perform. A new and promising method that has joined the diagnostic toolbox is a basophil activation test (BAT). Basophils, a particular type of white blood cell, secrete histamines and other inflammatory chemicals in response to a perceived threat, such as an allergen. Nadeau and her colleagues developed and patented a test that requires no more than one drop of blood, mixing it with the suspected allergen and measuring the basophil response. In running studies of this process, we diagnosed allergies with an accuracy of 95% in children and adults, a rate similar to that obtained in tests through food tasting.

The BAT method is still in the research stages and requires further experiments in a larger and more diverse population. But another approach, the "ingredient-allergen test", has already been approved by the US Food and Drug Administration for peanut sensitivity testing. Linda Schneider, a pediatrician specializing in allergies and director of the allergy program at Children's Hospital in Boston, says that there are children who have a mild sensitivity, but not a full-blown allergy, to one protein found in peanuts. Instead of testing the children using a crude mixture of many proteins found in peanuts, in Schneider's method, certain proteins are isolated and each of them is tested in front of the patients. By classifying the non-reactive proteins, doctors can determine with a high degree of accuracy whether the patient is truly allergic to peanuts.

Schneider wants to move beyond diagnosis and provide treatment as well. Omalizumab is a monoclonal antibody that binds to IgE antibodies and prevents them from reaching the mast cells that trigger the chain of allergic reactions. In a recent study, Schneider and her colleagues provided this drug, also known as anti-IgE, to 13 children who suffered from peanut allergy for 20 weeks. During the period they also gave the children increasing portions of peanuts. During the experiment, no child developed an allergic reaction to peanuts, although in two of them the symptoms returned when the anti-IgE treatment ended. "The anti-IgE allowed their system to undergo a process of lowering the level of sensitivity," says Schneider.

Byrd found that children with milk and egg allergies can also be gradually desensitized by heating these foods for about 30 minutes. The heating changes the shape of the proteins and thus greatly reduces their ability to trigger allergies. This is not a recipe for home treatment and it must be done under medical supervision, but studies show that children who are fed small amounts of heated eggs or milk are more likely to acquire tolerance to these foods over time, that is, they are more likely to be cured of the allergy. A study called "Early Learning About Peanut Allergy" (LEAP) showed that exposure of children to small amounts of peanut products early in their lives dramatically reduces the incidence of allergy. (The researchers used "Bamba" made in Israel - the editors.)

Scott H. Sicherer, a pediatrician specializing in allergies and immunology at the Icahn School of Medicine at Mount Sinai, takes the idea of ​​early desensitization one step further. He suggests that the best way to avoid allergies is to expose children to a wide variety of foods at a young age, run in the open air and "play in the dirt." A little less protection from the world, he says, is the best defense against allergies.

About the writers

Alan Rapel of Shell
Author of the book The High Cost of Discount Culture and is a partner in the graduate program in science journalism at Boston University.