Aeroallergens and Asthma

The main aeroallergens in both the indoor and outdoorenvironment that have been implicated in the pathogenesisof allergic asthma are reviewed. Pollen and fungal sporesare important outdoor aeroallergens that cause sensitizationin atopic subjects, leading to rhinitis and asthma in a proportionof the sensitized subjects. Each pollen type displays aparticular seasonal periodicity: tree pollen are prevalent inthe late winter and spring, grass in the spring and summerand weed mainly in the fall. There are regional differencesin the type of pollen grains in Canada. Although the pollengrains arc large fragments less than 10 µ can reach thelower airways to cause asthma. Some fungal spores. such asAlternaria and Cladosporium, have been implicated inasthma. The full clinical impact of fungi in asthma has yetlo be clarified. With the construction of homes that aretightly scaled to conserve heat and the use or wall to wallcarpet. the type and concentration of indoor aeroallergenshave become increasingly different from outdoors. Housedust mite and pet allergens have now been shown to heimportant acro:dlergcns that sensitize children in infancyand are risk factors for asthma. Clinicians should recognizethe importance of aeroallergens in asthma because avoidanceand/or reduc1iun of exposure is an important part of themanagement besides drug therapy