Exposure to farm dust may cause asthma, rhinitis, allergic alveolitis, organic dust toxic syndrome, and chronic bronchitis. Febrile reactions to inhaled dusts are common and are usually of a toxic rather than an allergic type. Some evidence indicates that dairy farmers may have an increased prevalence of chronic bronchitis, allergic asthma, rhinitis, and chronic airflow limitation, but this has not been conclusively shown. Storage mites and cow dander are important allergens in dairy farming. Inflammation of airways may in part be caused by immediate or delayed hypersensitivity. Other mechanisms, such as activation of inflammatory cells from toxic agents or high exposure levels, may be of considerable importance in causing airway and lung disease.