Allergen sensitization in children with asthma and rhinitis: marked variations related to age and microgeographical factors.

BACKGROUND Each region should know which its predominant allergens are. However, in addition to the differences that exist between different geographical areas, variations within the same area should be determined. OBJECTIVES To review the predominant allergens in the paediatric population suffering from asthma or rhinitis in our region and analyse the internal variations and associated factors. METHODS A cross-sectional, descriptive study reviewing all the patients having a diagnosis of asthma or rhinitis in the paediatric allergy units of three hospitals in a coastal region in the south-east of Spain between 2001 and 2006. RESULTS Data on 3066 patients, 2202 (72 %) of whom were atopic, were collected. Atopy was present in 63 % of asthmatics, 90 % of those with rhinitis and 95 % of those with both asthma and rhinitis. The percentage of atopic patients increased with age. Egg was the main allergen in the first 3 years of life, followed by milk. Aeroallergen sensitization started in the second year of life and increased rapidly in subsequent years. The main aeroallergens in our region, in descending order, were: olive, mites, Salsola, Alternaria, cat, dog and grasses. With the five main aeroallergens, 98 % of atopic patients between 6 and 14 years of age, and 94 % of those between 3 and 5 years of age are detected. In children under the age of three it is necessary to combine food and aeroallergens in order to detect most of the atopic patients. Sensitization to Alternaria occurred at an early age but stabilized before that caused by other aeroallergens. Sensitization to mites was very high along the coastline (83 %) but at only 5-30 km inland it decreased by half. On the other hand, sensitization to pollen and Alternaria increased sharply as we move away from the coast. CONCLUSIONS We have described the main allergens in children with asthma and rhinitis in a Mediterranean region in Spain, and have found marked differences depending on age and proximity to the coast. The local importance of Salsola, the early sensitization to Alternaria, and the surprisingly short reach of the influence of the coast in favouring sensitization to mites and protecting from sensitization to pollens and Alternaria are noteworthy.