The hypersensitivity disorder of the immune system in the human body is referred to as an allergic reaction. This occurs when the immune system reacts abnormally to substances that are normally harmless and present in the surroundings.
Types of Hypersensitivity
Hypersensitivity is formally known as type I (or immediate) hypersensitivity and is one of four or more types of hypersensitivity. The load of allergic diseases in India has been on a rising tendency in terms of prevalence as well as severity.
Prevalence of Allergic Diseases in India
Allergic diseases in India encompass a range of conditions, including asthma, rhinitis, anaphylaxis, drug, foodstuff and insect allergy, eczema, and urticaria and angioedema. Approximately 20% to 30% of the whole population suffers from at least one of these allergic diseases in India.
Historical Perspective
A study carried out over 30 years ago in Delhi reported around 10% allergic rhinitis and 1% asthma in 1964. Subsequent studies have indicated an alarming increase, revealing that 20% to 30% of the population now experiences allergic rhinitis, and 15% develop asthma.
Recent Studies
Recently, a multi-centre population study, Indian Study on Epidemiology of Asthma, Respiratory Symptoms and Chronic Bronchitis (INSEARCH), has also been conducted. The study covered 12 centres comprising both rural and urban areas spread over different parts of India.
Findings from INSEARCH
The prevalence of bronchial asthma pooled for all the 12 centres was found to be 2.05% (range, 0.4%–4.8%). Advancing age, smoking, household environmental tobacco smoke (ETS) exposure, asthma in a first-degree relative, and the use of unclean cooking fuels have been connected with increased odds of asthma.
Prevalence of Allergic Diseases in India
Asthma and upper respiratory tract disorders are the prevalent symptoms of chronic allergy, affecting a considerable population of all age-groups in all parts of India. They pose a considerable socioeconomic burden as a effect of a reduced quality of life. The most updated and revised estimate on the global epidemiology of atopic asthma under the Global Burden of Disease project suggested that around 334 million people are asthma victims.
Keeping rate with the worldwide epidemiology, the incidence of the allergic reaction in India is also rising at a disturbing rate as greater than 25% of the Indian population suffers from various types of allergy. 20–30% of the population suffers from allergic rhinitis and 15% of them developed atopic asthma based on a hospitalization-based survey which was carried out in India. In addition to asthma, the other types of allergy, for example atopic rhinitis, anaphylaxis, drug, foodstuff and insect allergy, eczema, wheals, and angioedema, were also on a increasing tendency in terms of epidemiological burden as well as severity in India. A multicentre population study performed by Jindal et al. in different parts of India, named the Indian Study on the Epidemiology of Asthma, Respiratory Symptoms and Chronic Bronchitis (INSEARCH), revealed that 20–30% of the Indian population was clinically diagnosed as a victim of allergic reaction. The study also predicted the frequency rate of asthma, chronic bronchitis, and allergic rhinitis to be 2.05, 3.5, and 3.3%, respectively. This study also included the population of patients suffering from a paediatric allergy in which 3.3% of children aged 6–7 years and 5.6% of children aged 13–14 years were diagnosed with allergic rhinoconjunctivitis. Another multicentre study performed by the Asthma Epidemiology Study Group of the Indian Council of Medical Research observed the occurrence of allergic rhinitis in approximately 20% of the population in India. The World Allergy Organisation (WAO) predicted that the pollen allergy prevalence of the whole population ranges between 10 and 40.
Molecular Allergology in India
Recent advances in molecular biology have contributed major progress in the field of allergen biology or more specifically the “molecular allergology.”
Focus on Hypersensitivity in India
Taking into account the sound rise in the prevalence of asthma and other hypersensitive diseases, India should now focus on designing tools and strategies for the improvement of assessment and management of hypersensitivity.
Utility of Recombinant Allergens
Recombinant allergens were shown to have immense utility in allergen characterization and understanding the immune mechanism of IgE-mediated disease. In addition to that, recombinant purified allergens have shown promise in designing improved therapeutics in the near future.
Global Characterization and Clinical Practices
Until now, more than 100 such molecular allergens have been characterized from different parts of the western world and are being used in clinical practices as diagnostic antigens.
Precision Medicine for Hypersensitivity Treatment
These advancements in biomedical technology are heading towards establishing “precision medicine” for treatment of hypersensitivity in which “personalized immunotherapeutics” will be available based on the disease phenotype of an individual patient.
Disparities in Molecular Allergology Research in India
As compared to such incredible development worldwide in the field of molecular allergology, there have been only a few reports on the molecular characterization of allergens prevalent on the Indian subcontinent.
Challenges in IgE Repertoire Estimation
It has led to the unavailability of the superior multiplexed assay system to estimate the intricacy of the IgE repertoire present in the sera of allergic patients of Indian origin. As a result, allergists are still relying upon out-of-date, less-characterized, and less-standardized allergen extracts.
Ensuring Access to High-Quality Allergen Sources
Since pharmaceutical-grade recombinant allergen preparation is comparatively exclusive, the current focus in India should be to make sure the accessibility of high-quality allergen sources and allergen extracts.
Caution in Allergen Database Interpretation
It is notable to state that all the entries in the WHO/IUS allergen database should not be strictly measured as the genuine sensitizers as some of these proteins are considered to display IgE reactivity merely due to cross-reactivity and therefore are not clinically appropriate.
Importance of Accurate Characterization
Accurate characterization of novel allergens is an important feature of molecular allergology. It is referred to as a multistep discovery approach consisting of serodetection, identification, purification, and finally the molecular characterization of individual allergen molecules (i.e., components) from a specific source.