Table 3.

Etiologic agents: allergens and irritants

Non-WRA	Sensitizer-Induced OA	Irritant-Induced OA
Allergens
Variable exposure over time.	Variable exposure over time.
Inhalation of allergens on particles.
Absorption from skin exposure can cause sensitization but not asthma.	Absorption from skin exposure may cause sensitization but not asthma.
Levels of exposure are an important risk factor.	Levels of exposure are an important risk factor.
Highest levels of exposure can lead to decreased sensitivity.	Risk is present even at low levels of exposure to high-molecular-weight and low-molecular-weight agents: a pragmatic approach is to aim for an excess risk below a certain percentage.
Irritant Exposures Inducing Asthma
Acute irritant high-level exposure.		Acute irritant high-level exposure.
Recurrent exposures to nonmassive levels.		Recurrent exposures to nonmassive levels.
Long-term low exposures.		Long-term low exposures.
Irritant exposures may have an adjuvant effect, increasing IgE-mediated responses (e.g., diesel exhaust).	Irritant exposures may have an adjuvant effect, increasing IgE-mediated responses (e.g., diesel exhaust).	Irritant exposures may have an adjuvant effect, increasing IgE-mediated responses (e.g., diesel exhaust).
Ascertaining exposures can be complex and can vary over time (e.g., cleaning agents).		Ascertaining exposures can be complex and can vary over time (e.g., cleaning agents).
Gene–environment interactions can occur.	Gene–environment interactions can occur.	Gene–environment interactions can occur.
Allergens and Irritants
Exposure controls may reduce risks of asthma onset and exacerbations.	Exposure controls may reduce risks of asthma onset and exacerbations.	Exposure controls may reduce risks of asthma onset and exacerbations.

Definition of abbreviations: OA = occupational asthma; WRA = work-related asthma.

Similarities are printed in bold. Features that differ or have only been only evaluated for one condition are not bold.