16th January 2024

Background

It is estimated that occupational asthma (OA) accounts for 9-15% of adult-onset asthma and is recognised as the most common cause of occupational lung disease worldwide. There are numerous recognised OA allergens. The two most common causes of OA in the UK are flour dust and isocyanates. High-risk occupations include cleaning, chemical processing, spray painting, metalworking, woodworking, plastic and rubber manufacturing and baking.

OA is defined as asthma secondary to immunological or non-immunological stimuli found in the work environment. Causative allergens are categorised as low molecular weight (LMW) and high molecular weight (HMW) proteins. The two recognised forms of OA include allergic OA and irritant-induced asthma (non-allergic). In allergic OA, repeated exposure to HMW proteins produces an IgE-mediated immune response. Level of exposure serves as the greatest risk factor for developing OA. Individual factors such as atopy, smoking history, and genetic factors predispose individuals to developing OA. Non-allergic OA is a result of bronchial hyperresponsiveness following exposure to an irritant substance and does not involve immunological sensitisation.