The potential toxicity of ingested metabisulfite is a source of great concern to patients with asthma. This problem is of particular interest to the wine industry because potassium metabisulfite has been used for centuries to sterilize the mold and bacteria found in barrels or tanks as part of fermentation. Although there have been many observations on the influence of wine in asthmatics, the vast majority reflects anecdoctal case reports. Because of the relationship of metabisulfite to wine, we challenged a group of 25 asymptomatic, normal individuals and 25 patients with asthma with 4 oz of white wine containing 160 mg% of metabisulfite. Pulmonary function tests were performed immediately before, and 20 minutes and one hour after drinking the wine. Of the asthmatics who completed the study, seven of 24 decreased their FEV1 more than 10% at 20 minutes, and five of 23 decreased their FEV1 more than 10% at one hour. Furthermore, four patients decreased their FEV1 from 23% to 36%. Two patients felt symptomatic and one required treatment with a metered aerosolized dose of Alupent. These two symptomatic patients were further studied to identify the mechanism involved by drinking in a blinded fashion either a "model wine solution," prepared on the chemists shelf without metabisulfite, or a "model wine solution" prepared with metabisulfite. One patient became symptomatic when he drank either "wine".(ABSTRACT TRUNCATED AT 250 WORDS)