Allergic diseases can affect several organs of the body like the eyes (allergic rhinoconjunctivitis), the nose (allergic rhinitis), the skin (atopic eczema or urticaria) and those that have multi-system involvement like food allergies, anaphylaxis, angioedema, eosinophilic disorders and drug and insect allergies. Also, allergic rhinitis acts as a risk factor for asthma and the lack of proper control of allergic rhinitis can lead to asthma.
Allergic diseases can be life-threatening like anaphylaxis, food allergies, certain forms of asthma, angioedema and drug and insect allergies. The prevalence of allergic diseases is rising and currently about 300 million people globally suffer from asthma, and according to the World Health Organisation, the number of patients having asthma is expected to increase to 400 million by 2025. Asthma alone causes 2,50,000 deaths a year.
Food allergies can occur in both children and adults and can manifest as skin rashes, respiratory (choking sensation, laryngeal oedema, breathlessness), gastrointestinal (nausea, vomiting and diarrhoea) or circulatory symptoms. Common food items causing allergies in children include cow's milk, egg, peanut, shellfish, fish, soyabean and wheat. In adults, it is shellfish, vegetables, fruits, peanuts, tree nuts and fish (in India, also chickpeas and lentils). Food allergies can lead to anaphylaxis, which can be fatal.
Anaphylaxis is a life-threatening generalised or systemic hypersensitivity reaction that can also be described as a serious reaction that is rapid in onset and may cause death. Potential triggers are food items, stinging insects and medication. Early recognition, diagnosis and treatment of anaphylaxis is crucial as the incidence appears to be increasing worldwide. Currently, the overall prevalence of anaphylaxis is estimated to be as high as 2 per cent. Most importantly, anaphylaxis is often under-diagnosed, increasing the risk of serious adverse events, including death. Also certain populations, such as patients with atopy, asthma patients, and the elderly are at a higher risk of anaphylaxis. However, allergic diseases commonly occur together in the same individual. This requires greater awareness of allergic disorders and their underlying causes, particularly for primary care physicians.
This rise in the prevalence of allergies is observed as societies become more affluent and urbanised. A variety of factors like an increase in environmental risk factors like outdoor and indoor pollution and reduced biodiversity also contribute to this rise in prevalence. There are also complex, but measurable associations between early-life circumstances (for example, maternal and childhood nutrition). Hence, many developing countries now find themselves in a stage of transition in which they face a growing burden of allergic diseases on top of the disease burden of malnutrition and communicable diseases. Abatement of many of the risk factors like indoor tobacco smoke, outdoor pollution and biomass fuel can have huge health benefits. Allergic diseases have an impact on the quality of life. Furthermore, owing to burdensome health care costs, disability, absenteeism and forgone income, allergic diseases result in a socio-economic burden to the affected families as well as countries. Confronted by the ever-increasing threat of such diseases, high-, middle-, and low-income countries need to come together to develop a common strategy to find solutions at the levels of policy, health care delivery, health communication and education.
Pawankar is president of World Allergy Organisation and is professor of allergy, department of paediatrics, Nippon Medical School, Tokyo.
1. Sampson HA, et al. J Allergy Clin Immunol. 2006;117:391-397
2. Pawankar R, et al. WAO White Book on Allergy (World Allergy Organization), 2011