Sulphites are preservatives used in the production of some foods and drinks. The Romans first discovered that adding sulphites to foods makes them last longer, and helps preserve their colour and flavour.
Can sulphites cause allergy?
Generally speaking, it’s quite rare for someone to be allergic to sulphites. However, sulphites can cause allergy-like symptoms in people with underlying asthma and allergic rhinitis - the most common reactions being wheezing, having a tight chest and coughing.
Severe reactions to sulphites (anaphylaxis) have been reported but are very rare and some people with urticaria, a type of skin rash, can also experience worsening of symptoms after eating sulphites.
How do sulphites cause symptoms?
Sulphites work as food preservatives by releasing sulphur dioxide, a gas, which is an irritant that can cause the airway to become irritated and constricted. It’s thought that in most people sensitive to sulphites, the gas is released when sulphite-containing foods interact with acid in the stomach, dispersing into the stomach but also back up and into the airway, causing symptoms.
What foods and drinks contain sulphites?
Sulphites are important, as they help preserve many foods and drinks and prevent them from going off. They are also used in the production of most wines, as they stop the fermentation process, which would otherwise make the wine turn sour.
Foods which may contain added sulphites include (check labels):
• pickled foods and vinegar
• dried fruit e.g. dried apricots, prunes, raisins etc
• maraschino cherries
• tinned coconut milk
• beer, wine and cider
• vegetable juices
• some soft drinks
• grape juice
• bottled lemon juice and lime juice
• condiments (bottled sauces etc.)
• dehydrated, pre-cut or peeled potatoes
• fresh or frozen prawns
• some processed meat products
The following food additives contain sulphites; the same chemicals may be found in medications or cosmetics:
• E220 Sulphur dioxide
• E221 Sodium sulphite
• E222 Sodium hydrogen sulphite
• E223 Sodium metabisulphite
• E224 Potassium metabisulphite
• E226 Calcium sulphite
• E227 Calcium hydrogen sulphite
• E228 Potassium hydrogen sulphite
• E150b Caustic sulphite caramel
• E150d Sulphite ammonia caramel
Do medicines contain sulphites?
Sulphites are sometimes used in medicines, as a preservative. These can include topical creams and eye drops, however since most people only react to sulphites when the substance comes into contact with acid in the stomach, it’s rare for these medicines to cause any adverse effects.
Some injection drugs (especially local anaesthetics) contain sulphites as a preservative, so if you are sulphite sensitive, ask your pharmacist to check that your medicine is sulphite-free. Check the ingredients on the patient information leaflet for any medicines given to you, including those that you buy yourself over-the-counter.
Sulphites in cosmetics
Sulphites may be present in hair colours or bleaches, skin lighteners, fake tanning lotions, body lotions, shampoos and shower washes, moisturisers etc.
Most people with sensitivity to sulphites will not have a positive allergy test, and keeping a food diary to show to your healthcare professional will help them to make a diagnosis. Sometimes, your health professional may recommend an elimination diet of foods containing sulphites, which may be followed by a food challenge, but this should only happen under medical supervision.
Once the diagnosis has been made, treatment consists of avoidance of sulphite-containing foods, medicines and cosmetics. While some people who suffer from mild sensitivity will only need to avoid foods containing the highest sulphite content, others with more severe sensitivity will need to be careful in avoiding even trace amounts in foods, medicines and cosmetics.
Some manufacturers produce test kits which can detect the presence of sulphites in food and drink, however, these are not 100% reliable. If you are sensitive to sulphites, the most important thing is to know how to treat your symptoms and be able to do so when, for example, you are eating away from home.