Occupational asthma

Occupational asthma is an allergic reaction that can occur in some people when they are exposed to substances, for example flour or wood dust in the workplace.

These substances are called 'respiratory sensitisers' or asthmagens. They can cause a change in people’s airways, known as the 'hypersensitive state'.
Not everyone who becomes sensitised goes on to get asthma. But once the lungs become hypersensitive, further exposure to the substance, even at quite low levels, may trigger an attack.
The main causes of occupational asthma are set out in Section C of HSE's Asthmagen Compendium.
This list of substances is a useful summary. Also look for the risk phrase R42 ‘May cause sensitisation by inhalation’ on product labels or safety data sheets.