The allergen selection for immunotherapy is one of the most important clinical decisions in the entire treatment process, because immunotherapy works by modifying the immune response to a specific allergen, and it only works for allergens that are confirmed to be clinically relevant to the child's disease. Including allergens that the child is not sensitised to adds nothing. Missing allergens that are actually driving the child's symptoms will produce incomplete benefit. The decision is made through a combination of the clinical history, skin prick testing, and in selected cases specific serum IgE testing. Skin prick testing is the primary diagnostic tool. A small amount of standardised allergen extract from a panel of allergens relevant to the Varanasi region is placed on the forearm and introduced through a gentle prick in the skin. A positive test produces a wheal, a raised, itchy bump at the site, within fifteen to twenty minutes, indicating IgE-mediated sensitisation to that allergen. The allergens I test in Varanasi include house dust mite (Dermatophagoides pteronyssinus and Dermatophagoides farinae, the two most common HDM species), cockroach, local grass pollens, local tree pollens, weed pollens relevant to the Uttar Pradesh region, moulds, and animal danders where relevant. The results of skin prick testing tell me which allergens the child's immune system has sensitised against. But sensitisation alone is not sufficient to determine the immunotherapy formulation: I also need to establish that the sensitised allergen is clinically relevant, meaning that the child's symptoms occur or worsen with exposure to that specific allergen. A child who tests positive to grass pollen but whose symptoms are identical in grass season and out of it may have a primary HDM problem, not a grass problem. The clinical history and the skin prick test together establish which allergens are driving the disease, and only those allergens are included in the immunotherapy extract. At Vatsalya Hospital, Varanasi, I always go through the skin prick test results in detail with the family, explaining which sensitisations are clinically relevant and why those specific allergens have been selected for the immunotherapy formulation.
Written by Dr. Divyank Pathak, MBBS, MD (Paediatrics), IFPCCM, DPAA, FNPP, DPSM, FAAP, Director and Senior Consultant Paediatrician, Pediatric Critical Care and Allergy and Asthma Specialist, Vatsalya Superspeciality Children Hospital, Varanasi 221002. Phone: +91 9838713111.
