Introduction: Irritant asthma, irritant rhinitis, and related conditions

Abstract

Inhaled substances produce airway inflammation by two well-defined and distinct mechanisms. Aeroallergens are proteins on airborne particles that induce IgE antibodies with a high affinity for mast cells and basophils. Exposure causes degranulation and the release of inflammatory mediators. Respiratory irritants are chemicals that bind to chemoreceptors on sensory nerve fibers, leading to the release of mediators of neurogenic inflammation. Clinical manifestations are independent of the mechanism, have intra- and interindividual variability, and range from rhinorrhea and congestion in the upper airway to bronchospasm and bronchorrhea in the lower airway. Acute exposures to respiratory irritants are known to induce persistent upper and lower airway inflammation that have been termed reactive airways dysfunction syndrome and reactive upper-airway dysfunction syndrome, respectively. The mechanism is a remodeling of the structure of the airway mucosa, leading to pathological changes that lower the threshold for irritant sensitivity, so that chronic inflammation is induced by ongoing previously tolerated exposures.