Role of insects as inhalant allergens in bronchial asthma with special reference to the clinical characteristics of patients

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Abstract
The whole body extracts (WBEs) of 13 common insects from Delhi (India), namely Musca domestica (house fly); Sitophilus oryzae (rice weevil); Callosobruchous maculatus (pulse beetle); Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti (mosquitoes); Blattella germanica and Periplaneta americana (cockraoches: male, female and nymph); Spodoptera litura and Heliothis armigera (moths), was prepared to evaluate their allergenic significance in patients with allergic bronchial asthma. Intradermal (ID) tests were performed with these WBEs on 75 patients with bronchial asthma and 20 healthy non-allergic volunteers. An ID test was considered positive when the weal diameter was more than twice that of phosphate-buffered saline control and at least 6 mm in size and an erythema of more than 15 mm. In the patients 27.7% of the ID tests performed were total positive (1+ to 4+) as compared to 7.1% in the controls. Ten point two per cent of ID responses were markedly positive in asthmatics (2+ to 4-) as against none in controls. Of the 13 bronchial provocation tests (BPTs) performed on patients giving positive cutaneous responses, eight (61.5%) were positive. Similarly, RASTs were positive in 87.5% of the limited sera tested from the patients with positive ID responses. The patients with a positive family history of allergic disorders gave higher percentages of positive ID responses as compared to the asthmatics with no family history. Similarly, the ID positivity was significantly higher in patients with associated allergic disease like allergic rhinitis as compared to the patients with bronchial asthma alone. Interestingly, we observed significantly higher ID responses to insects in seasonal asthmatics. Thus, we conclude that insects do play an important role in the aetiology of allergic bronchial asthma, and that allergy to insects has a significant bearing on the clinical characteristics of these patients.