The wheezy child.

Wheezing in association with viral respiratory tract infections occurs in 10-20% of all infants and young children and usually indicates hyperreactive bronchi. Signs of airway hyperreactivity can usually be demonstrated many years after the child has stopped wheezing. This hyperreactivity is partly constitutional, but it may be further aggravated by viral infections in the respiratory tract. Similarly, allergic inflammation or long-term exposure to airway irritants may also cause or aggravate a state of hyperreactivity which may be expressed as a proneness to asthmatic reactions. As viral infections are among the most potent asthma-provoking factors known, the hyperreactivity does not need to be very pronounced before wheezing develops in the infant or young child, with its small-calibred airway. As long as wheezing only occurs sporadically and only in association with viral respiratory tract infections, the prognosis is usually excellent. However, recommendations regarding avoidance of potent allergens and airway irritants in the daily environment should be given to such families. Such advice is especially important for families with a proneness to atopic reactions or if wheezing begins to occur even during infection-free periods.