Face your fears

Food allergy dictates eating low doses of the very food daily  

By Tiasa Adhya
Published: Friday 30 April 2010

imageARNAB SEN is prone to allergies. His first bite of fried prawn helped him understand what it meant. Benadryl, a syrup for cough brought things under control but with the next reaction Sen was in the nursing home. The seven-year-old studies in elementary school in Kolkata.

Anaphylaxis is a serious allergic condition that does not give the body time to react. Symptoms may include difficulty in breathing, dizziness or loss of consciousness. Without immediate treatment, an injection of epinephrine (adrenalin) and expert care, it can be life threatening. But how anaphylaxis is triggered is still a mystery.

When Sen bit into the prawn, for some unclear reason his body perceived the protein content of the animal as trouble. His immune system released an antibody called IgE (immunoglobulin E) which attached itself to the mast cells in tissues throughout Sen’s body. How did Sen’s body let him know this was happening? He turned red, swelled like a sea sponge, and choked on the mouthful. “Things happened so quickly, he swelled, his throat pained. My little boy was gasping for breath”, said Sen’s mother. But it did not end there.

The human body has its own diary to pen down memories. The IgE molecules, once attached to the mast cells, stay that way forever—wary sentinels waiting for war. With the second exposure, the mast cells in Sen’s body released a cascade of chemicals: histamine, prostaglandins, and leukotrienes, which caused inflammations, worked the nerve endings into a frenzy making him itch all over, contracted his muscles, acted on glands that released mucus, dilated his blood vessels that lowered his blood pressure. The result: a day at the nursing home.

“About 250 million Indians suffer from one or more allergic diseases whereas only 60 million are suffering from cardiac problems,” said Wiqar Ahmed Ibrahim Shaikh, the medical director of the non-profit National Allergy and Asthma Campaign in India. “The sale of anti-histamine (anti-allergic) tablets is between Rs 600 crore- Rs 800 crore per year in India,” he added. “About 40 per cent of the global population has food allergies. It affects 24 per cent of the population in the United Kingdom, 20.6 per cent in Norway and 19.6 per cent in Germany,” said Ruby Pawankar, the first Indian to become a member of the World Allergy Organisation.

Beat allergy with the allergen

The causes of anaphylaxis have been studied by very few. One on Eosinophilic esophagitis (EoE), a type of allergic disorder, was carried out recently. EoE is discovered in children when their throats bulge and food tracts swell leaving them unable to swallow their food. This is because of the accumulation of eosinophils, immune system cells, in the food pipe leading to its inflammation. The study was published online on March 8, 2010 in Nature Genetics. Carried out by Hakon Hakonarson, director of the Center for Applied Genomics at The Children’s Hospital of Philadelphia in USA, it linked EoE to a region of chromosome five that includes two genes. The likely culprit is the gene TSLP which has been linked to allergic inflammatory diseases like asthma and skin inflammations such as atopic dermatitis.

In most cases, EoE can be treated by introduction of a simple diet that lacks any allergenic food proteins. This means Sen would have to forgo prawns. A research from the Johns Hopkins Medical Institutions in USA suggests this might not be necessary, though. Their study on children with milk and egg allergies showed by facing a bit of the allergen everyday and in increasing doses the immune system of children like Sen “learn” to tolerate the food without triggering an allergic shock.

The researchers placed small but increasingly higher doses of the milk proteins under the patients’ tongues (sublingual immune therapy). Nine out of 10 children who were treated with milk drops under the tongue for several weeks were able to drink seven times more milk with just mild symptoms. In the other study carried out over 11 months, 40 patients, aged five to 18, were given increasingly higher doses of egg whites (oral immunotherapy), while 15 children were given “dummy” egg whites that contained no egg protein. At the end of the study, 21 of those 40 could tolerate five grammes of eggs without an allergic reaction and just mild symptoms involving itching of the mouth and throat. The other 15 were not able to tolerate eggs.

“We are excited to see these approaches can achieve significant improvement in children with milk allergies. We also see slightly better tolerance in children on oral immunotherapy,” said lead investigator Robert Wood, director of Allergy and Immunology at Hopkins Children’s. The findings were presented on February 28 at the annual meeting of the American Academy of Allergy, Asthma & Immunology in New Orleans, USA. With such developments Sen might not have to give up on prawns after all.

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