Clinical implications of bronchial hyperreactivity.

Bronchial hyperreactivity may be a primary internal factor needed for the occurrence of asthmatic symptoms when the atopic individual meets with allergens or the non-atopic individual inhales irritants causing inflammatory reactions in the bronchial tree. It can also be a secondary expression of allergy and occupational exposures. The hyperreactivity can be affected by treatment and is therefore a valuable tool to judge experimental studies of background and predictive factors, for follow up of specified airways disease and for treatment and drug effects. It is necessary to collect sufficient background factors and to use proper dose-response studies. We still lack knowledge as to why presumed normal subjects react, is it due to undetected small airways disease? Do we need to measure both sensitivity (as threshold values) and reactivity (as dose response-curves) in all kinds of tests of bronchial reactivity? We need simple ways to test larger populations in prospective studies of workers exposed to occupational irritants in order to solve the problems of primary versus secondary, acquired hyperreactivity.