Sulphur dioxide in foods and beverages: its use as a preservative and its effect on asthma.

Sulphur dioxide is widely used in the food and drinks industries for its properties as a preservative and antioxidant. Whilst harmless to healthy persons when used in recommended concentrations, it can induce asthma when inhaled or ingested by sensitive subjects, even in high dilution. About one in nine asthmatics gives a history of asthma worsened by drinking 'soft drinks' containing sulphur dioxide. They are comparatively young and their asthma is predominantly extrinsic. The amount of sulphur dioxide in foods is limited by regulation in the UK, by directive in the EEC, and by recommendations to 'good manufacturing practice' in the USA. A list is given of foods and beverages commonly containing sulphur dioxide. These are predominantly dried fruits and vegetables, soft drinks and alcoholic beverages. Maximal permitted concentrations are quoted. Exposure to sulphur dioxide may also occur during the manufacture and preparation of foods and drinks in the factory, restaurant and home.