Neurogenic inflammation produced by neuropeptides released from sensory nerve endings to the airways is a proposed common mechanism of association between both allergic and non-allergic rhinitis with asthma. This may explain higher association of rhinitis with asthma developing later in life.  Environmental irritants acts as modulators of airway inflammation in these contiguous airways. Development of occupational asthma is often preceded by occupational rhinitis. Among the causative agents are flours, enzymes used in processing food, latex, isocyanates, welding fumes, epoxy resins, and formaldehyde. Accordingly, prognosis of occupational asthma is contingent on early diagnosis and the adoption of protective measures for rhinitis.