The common cold is a viral disease with predominant symptoms from the upper airways. Rhinovirus is the most important common cold virus, and rhinovirus infection is predominantly transmitted by direct contact (nasal secretion-hand (object)-hand-mucous membrane in eye and nose). The viral disease results in the release of IL-8 from nasal epithelial cells, causing a neutrophil-dominated inflammation in the nose. The biochemical mediators, causing nasal symptoms, have not yet been identified. A common cold is the most important cause of exacerbations of asthma in children and also in adults. The rhinovirus infection induces airway inflammation, bronchial hyperresponsiveness and asthma symptoms. However, the mode of action of the virus-induced inflammation on the asthma disease is poorly understood. As a routine, physicians give oral corticosteroid and increase the dosage of inhaled corticosteroid during a common cold-induced exacerbation of asthma, but there do not seem to be any placebo-controlled trials in support of this practice.