Acute bronchitis is usually caused by infectious agents such as bacteria or viruses. It may also be caused by physical or chemical agents − dusts, allergens, strong fumes, and those from chemical cleaning compounds, or tobacco smoke. (Acute asthmatic bronchitis may happen as the result of an asthma attack, or it may be the cause of an asthma attack.)
In children, the most common cause of bronchitis is a virus, although in children over 6 years of age, it can be caused by bacteria. Acute bronchitis is usually a mild condition. Acute bronchitis may follow the common cold or other viral infections in the upper respiratory tract. It may also occur in children with chronic sinusitis, allergies, or those with enlarged tonsils and adenoids. Pneumonia is a complication that can follow bronchitis.