Risk factors and epidemiology.

What we know: No one gene is a major cause of asthma. Some racial groups are more at risk of asthma than others. Early exposure to domestic animals appears to reduce the chance of developing asthma. Good hygiene may increase the likelihood of asthma. Impaired early airway function predisposes to asthma. What we need to know: How do several minor genetic factors combine to increase the risk of asthma in individuals and in population groups? Does early exposure to allergens promote sensitisation or tolerance? How do viruses precipitate asthma? Can acute asthma be treated by treating viral respiratory infections? Does impaired early airway function predispose to asthma throughout childhood?