One has granules that stain pink named eosinophils after the Dawn Goddess Eos. There are groups of asthmatic patients. Their asthma is episodic and comes on when pollens or molds from wet leaves are airborne. Asthma developing late in life tends to be nonallergic without positive skin tests. Exposure to industrial pollutants like sulfur dioxide during thermal inversions makes all kinds of asthma worse but possibly can cause asthma newly in people without lung disease.
Smoking does the same thing.
Baker's asthma caused by reaction to wheat flour is one of a family of occupational asthmas including woodworkers, photographers, metal workers, solderers, farmers, plasticiser's, and printers asthma. A weekend free of asthma suggests occupational asthma. This is less obvious in hobby workers asthma. The viruses probably loosen the tight junction between lung tube lining cells and allow allergens to trigger bronchial muscle spasm. Exercise can start an attack of asthma.