Asthma with sulfite intolerance in children: a blocking study with cyanocobalamin.

Sulfites have been implicated as the cause of bronchospasm in some subjects with asthma. However, there is still no universally accepted explanation of the pathogenesis of these reactions. We have studied five children with asthma with metabisulfite intolerance confirmed by oral challenge testing. The challenge test with metabisulfite was repeated after premedication of all the patients with 1.5 mg of oral cyanocobalamin. In four of the five patients treated with cyanocobalamin, bronchospasm did not develop in the second metabisulfite challenge. The possible mechanisms are discussed.