Metabisulfite oral challenge: incidence of adverse responses in chronic childhood asthma and its relationship with bronchial hyperreactivity.

Fifty-six children with chronic asthma, 6 to 14 years of age, were studied to evaluate bronchoconstrictive airway responses after ingestion of varying doses of potassium bisulfite administered in one occasion in capsule and in another occasion in solution. With methacholine challenge before and after metabisulfite (MBS) provocation, the relationship of bronchoconstrictive responses and bronchial hyperreactivity was evaluated. Positive bronchoconstrictive responses were observed in only four children after the ingestion of a maximum dose of MBS in capsule and in two children after the ingestion of different doses of MBS solution. A high reactivity to methacholine challenge was present in all the reactive children. After MBS challenge, no additional changes in bronchial reactivity were observed either in the reactors or nonreactors.