flower pollen and allergic reaction. pollen spores as allergens on the human mucosa

air airborne allergen allergenic allergens allergic allergy asthma asthmatic biology botany breath breathing care cell disease diversity dust exposure fever flower flu forecast germ grain hay headline health human ill illness illustration immune irritants macro medicine microscopic mucosa nasal nature nose particle plant pollen pollination pollinosis reaction research rhinitis season seasonal sky spore spores summer