Individuals with occupational asthma caused by high-molecular weight allergens (HMWA) have a milder clinical course and are able to maintain and continue jobs with harmful occupational exposure compared with patients with asthma induced by low-molecular weight allergens (LMWA), study results in Allergy, Asthma & Immunology Research suggest.

A total of 200 patients underwent a single inhalation challenge (SIC) of workplace allergens by spirometry and were also assessed with regard to methacholine challenges for the diagnosis of occupational asthma. Methacholine before and after SIC was used to evaluate nonspecific bronchial hyperresponsiveness. Patients were characterized by having either HMWA-induced asthma (n=130) or asthma induced by LMWA (n=70).

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Patients with HMWA-induced asthma were older (51 vs 40 years; P <.01), were more frequently active smokers (49.2% vs 22.9%; P <.01), showed lower level of nonspecific bronchial hyperresponsiveness (54.6% vs 81.4%; P <.01), and more frequently continued their work in jobs with harmful occupational exposure (63.1% vs 44.3%; P =.01).

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Asthma induced by HMWA was associated with more frequent occurrence of a single early bronchial response (ie, early phase bronchoconstriction) compared with patients with LMWA-induced asthma (86.2% vs 20%, respectively; P <.01). There were more frequent isolated late bronchial responses in patients with LMWA-induced asthma vs patients with HMWA-induced asthma (45.7% vs 3.8%, respectively; P <.01).

Patients with LMWA-induced asthma also had more frequent atypical patterns of bronchial obstruction compared with patients with HMWA-induced asthma (34.3% vs 10%, respectively; P <.01). In addition, the researchers more often detected baseline nonspecific bronchial hyperresponsiveness prior to SIC in patients with LMWA-induced asthma (81.4% vs 54.6%; P <.01). There was also a more frequent 3-fold increase in nonspecific bronchial hyperresponsiveness following SIC in LMWA-induced asthma compared with HMWA-induced asthma (82.8% vs 66.1%, respectively).

A study limitation was the lack of data on fractional exhaled nitric oxide during the SIC of workplace allergens.

The researchers emphasized in their conclusion that “there may be a possibility of job continuation despite requiring individual medical surveillance in HMWA-induced asthmatics.”


Lipińska-Ojrzanowska A, Nowakowska-Świrta E, Wiszniewska M, Walusiak-Skorupa J. Bronchial response to high and low molecular weight occupational inhalant allergens. Allergy Asthma Immunol Res. 2020;12(1):164-170.