New Delhi, Aug 5: A 13-year-old Indian-origin boy in London died last month after suffering a severe allergic reaction to a piece of cheese. According to media reports, Karanbir Cheema was allergic to wheat, gluten and dairy and his condition was well known at school but he came in contact with the allergen in cheese as it was allegedly forced on him by a schoolmate. Food allergy or intolerance, which can cause symptoms ranging from a harmless skin rash to a potentially lethal anaphylactic shock, are estimated to affect four to six per cent of children and four per cent of adults, according to the US Centers for Disease Control and Prevention (CDC). If left untreated, a food allergy can turn fatal, especially in children, because the body's immune system considers the proteins and complex carbohydrates present in the food as foreign. "It is only in rare cases that one can get a severe allergic response to any food allergen. Food items like cheese have other ingredients which may have caused severe allergic reaction. Commonly mild allergy, however, does not cause such severe reactions," Vivek Raj, Director (Gastroenterology), Max Super Speciality Hospital, told IANS. According to the US Food and Drug Administration (FDA), there are eight foods that are common for allergic reactions in a large segment of the sensitive population. These include, peanuts, tree nuts, eggs, milk, shellfish, fish, wheat and their derivatives, soy and their derivatives, and sulphites (chemical-based, often found in flavours and colours in foods) at 10 parts per million (ppm) and over. These can cause several types of allergies such as skin manifestations which include rashes, swelling and itching, respiratory symptoms including wheezing, bronchospasm and choking and gastrointestinal symptoms including cramping, vomiting and diarrhoea. Some also cause low blood pressure which manifests as light-headedness, dizziness or even a fainting spell. Allergy to any food item may cause bronchial secretions, which can lead to bronchospasm -- a sudden constriction of the muscles in the walls of the bronchioles in the respiratory tract. "As a result, the patient experiences choking and breathing difficulty, which, if not treated timely, may increase the risk of death," added Rakesh Gupta, Senior Consultant (Internal medicine), Apollo Hospitals. Further, children are much more vulnerable to food allergies than adults as the allergies fade away by adulthood. "As children grow older, they outgrow some of the allergies as their immune system matures. Also, the allergens are identified in childhood and then the person learns to avoid those as an adult," Raj noted. However, allergies are not just hereditary but may be related to gender, according to recent research published in the Journal of Allergy and Clinical Immunology. The study revealed that the genetic risk of a child having allergies doubles if the parent of the same sex is an allergy sufferer. Thus, mothers pass the risk of allergies to their daughters, as do fathers to their sons. Moreover, food allergies can worsen other conditions such as asthma and diabetes. If a patient already has other allergy-linked conditions like asthma, then the impact of food allergy can be more, doctors said. Therefore, an early identification of allergen and then complete avoidance of those allergens is essential. "As there is no cure to food allergy, the only way to prevent it is not to eat that food item," Ritika Samaddar, a Delhi-based nutritionist, told IANS. "The allergy can be confirmed by skinprick tests and/or bloods tests to measure the allergy antibodies," she added. Because fatal and near-fatal food allergy reactions can occur at school or other places outside the home, parents of a child with food allergies need to make sure that their child's school has a written emergency action plan. The plan should provide instructions on preventing, recognising and managing food allergies and should be available in the school and during activities such as sporting events and field trips, experts suggested. However, "if any allergic item is consumed, the patient should be immediately rushed to the hospital. No drug should be taken without a doctor's prescription", Gupta said.