When sulphites are present in a final food in amounts more than 10 ppm (parts per million), the food label must carry the chemical name and purpose of the additive (for example, potassium bisulphate as a preservative). Food-labelling protection regulations exclude sulphite-treated foods that are served as ‘fresh’, such as salad-bar ingredients, and menu items that are delivered to restaurants pre-prepared. Here, sulphites are used to preserve, for example, the crispness of green salads, or the whiteness of peeled, uncooked potatoes.

Asthma can also be triggered by the preservative sodium benzoate (found in fruit juices, soft drinks and foods with fruit), colourants like tartrazine, flavour enhancers like MSG (monosodium glutamate) and salicylates (found in aspirin).

The prevalence of food anaphylaxis due to masked allergens contaminating certain manufactured products has increased over the last 10 years. One study, which aimed to test levels of sensitivity to egg, peanut, milk and sesame seed, showed that respiratory symptoms were observed in 12 per cent (egg), 20 per cent (peanut), 10 per cent (milk) and 42 per cent (sesame), with subjects being highly sensitive to relatively low levels of the allergens.