We’ve heard of smoke, pollen and exercise being asthma triggers, but what about sulphites? This lesser-known trigger has been shown to cause wheezing, chest tightness and coughing in a small number of people with asthma.
Sulphites are naturally occurring in some foods but are widely used as a food additive to prevent microbial spoilage and preserve colour. Sulphites extend the shelflife by preventing or slowing down the growth of microorganisms, like mould or bacteria. Sulphites release sulphur dioxide gas (SO2), which is the active component that helps preserve drinks, foods and medication.
Sulphites can be found in soft drinks and cordials, dried fruit (especially dried apricots), wine, fermented foods, and processed products such as sausages and hamburger patties.
Under the Food Standards Code, added sulphites must be declared on the label of a packaged food when present in foods in concentrations of 10 mg/kg or more with the following additive numbers:
You can also test for sulphites using sulphite testing strips. These test for sulphite ions in water-based solutions. You can purchase these from allergy stores online.
The use of preservatives is regulated in New Zealand and can only be added to specified foods. They also can’t exceed the maximum permitted level (MPL) given in the Australia New Zealand Food Standards Code and the Food Act 1981.
The Ministry for Primary Industries has the statutory obligation to ensure food safety standards are being met.
It’s estimated between five to 10 percent of people with asthma may have adverse reactions to sulphites, resulting in wheezing, chest tightness and coughing. These symptoms are more likely when asthma is poorly controlled.
However, most people with sulphite sensitivity do not have positive allergy tests and there is currently no reliable blood or skin allergy test for sulphite intolerances. A food challenge under the supervision of a clinical immunology/allergy specialist may confirm or exclude sensitivity.
Sulphites can be found in a variety of foods and beverages. We have listed a few of these common items below.
Dried fruit such as apricots and pineapples are among the foods highest in sulphites, with raisins and prunes containing between 500 and 2,000 parts per million.
Pickles, relishes and foods made with vinegar, except distilled white vinegar, contain sulphites.
To preserve the life of the potato, many pre-cut and processed potato items such as crisps and chips contain sulphites.
Sulphites naturally occur in the grapes and hops used to make wine and beer. They prevent the growth of the bacteria that make the drink go cloudy and literally turn the alcohol into vinegar.
Soy protein products like soy sauce and tofu have naturally occurring sulphites as part of the fermenting process.
Jam preserves, jellies, and marmalades all contain sulphites due to the pectin gelling agent they contain.