why do workers of sericulture industry often develop asthma ,chronic bronchitis and difficulty in breathing?

The workers of sericulture industry often develop asthma ,chronic bronchitis and difficulty in breathing due the liberation of allergy causatives during the development of silkworm. The allergens from the silk worm excrete, silkworm cocoon, scales and the cuticles of the abdomen and wings of the silk moth are the main causative agents of the asthma and other respiratory problems.