Note: This document uses spelling according to the Australian Therapeutic Goods Administration (TGA) approved terminology for medicines (1999) in which the terms sulfur, sulfite, sulfate, and sulfonamide replace sulphur, sulphite, sulphate and sulphonamide.
Sulfites are preservatives used in some drinks, foods and occasionally medication. Sulfites can cause allergy like reactions (intolerances), most commonly asthma symptoms in those with underlying asthma, sometimes allergic rhinitis (hay fever) like reactions, occasionally urticaria (hives) and very rarely, anaphylaxis (severe allergic reaction). Wheezing is the most common reaction.
Sulfites are preservatives
Sulfites have been used since Roman times to preserve food flavour and colour, inhibit bacterial growth, reduce spoilage, stop fresh food from spotting and turning brown and help preserve medication and increase shelf life.
How do they work?
Sulfites release sulfur dioxide, which is the active component that helps preserve food and medication.
Asthma is the most common adverse effect
The most common adverse reactions, including wheezing, chest tightness and coughing are estimated to affect 5 to 10% of people with asthma. Symptoms are more likely when asthma is poorly controlled. However, adverse reactions to sulfites can also occur when there is no preceding history of asthma. Reactions can be mild through to potentially life threatening.
Anaphylaxis is much less common
Anaphylaxis has been described, but is very rare. Symptoms include flushing, fast heartbeat, wheezing, hives, dizziness, stomach upset and diarrhoea, collapse, tingling or difficulty swallowing.
Sensitivity to sulfites is a different condition from sulfonamide antibiotic allergy
Some patients will have allergic reactions to sulfonamide molecule-containing medication or sulfonamide antibiotics. This is a very different condition from sulfite sensitivity and is covered in a separate article: Sulfonamide antibiotic allergy.
The mechanism by which reactions occur is unclear
- Sulfur dioxide gas (SO2) is an irritant, and so reflex contraction of the airways from inhaling sulfur dioxide gas is one possible explanation. This mechanism may explain the rapid onset of symptoms when drinking liquids like beer or wine, when SO2 gas is inhaled during the swallowing process.
- Some people with asthma who react to sulfites have a partial deficiency of the enzyme sulfite oxidase which helps to break down sulphur dioxide.
- Some people (but not many) have positive skin allergy tests to sulfites indicating true (IgE-mediated) allergy.
Diagnosis of suspected sulfite sensitivity
Most people with sulfite sensitivity do not have positive allergy tests and there is currently no reliable blood or skin allergy test to test for sulfite intolerances.
At times, it may be important to undertake a deliberate food challenge with sulfites in a graded fashion under medical supervision to confirm or exclude sensitivity.
Information on food intolerances is available on the ASCIA website: Food intolerances
Sulfites are present in many foods
Sulfites have a useful role to play in helping preserve many foods and beverages. The addition of sulfites to some foods like beer and wine is permitted in most countries. In many countries, it is illegal to add sulfites to foods like fresh salads or fruit salads, or to meats like mincemeat or sausage meat. Unfortunately, these can be added from time to time illegally. The following is a list of the most common sources of accidental exposure to sulfites.
Drinks - cordials, some fruit juices, beer and wine, some soft drinks, instant tea.
Other liquids -- commercial preparations of lemon and lime juice, vinegar, grape juice.
Commercial foods -- dry potatoes, some gravies and sauces and fruit toppings, maraschino cherries, pickled onions, Maple syrup, jams, jellies, some biscuits and bread or pie or pizza dough
Fruit -- dried apricots, and sometimes grapes will be transported with sachets of the sulfite containing preservative. (Dried sultanas do not normally contain sulfites).
Salads and fruit salads -- sometimes restaurant salads and fruit salads will have sulfites added to preserve their colour.
Crustaceans -- sulphur powder is sometimes added over the top of crustaceans to stop them discolouring.
Meat -- sulfites are sometimes added illegally to mincemeat or sausage meat.
Other foods -- gelatin, coconut
The presence of sulfites can be recognised on labelled food
By Australian law, the presence of sulfites must be indicated on the label by code numbers 220 to 228, or the word "sulfite":
220 -- sulphur dioxide
221 -- sodium sulfite
222 -- sodium bisulfite
223 -- sodium metabisulfite
224 -- potassium metabisulfite
226 -- calcium sulfite
227 -- calcium and bisulfite
228 -- potassium bisulfite
Low or no sulfite wines and beers
Sulfites are generally found at higher levels in the cask wine than bottled wine, and are at much higher concentrations in white wine than red wine, which is preserved by natural tannins. Some wine makers in Australia produce wines that state that they do not add sulfites into the wine. Some brewers produce beer and state that they do not add sulfites. There are various technical reasons related to wine making and brewing, which may mean that very low levels of sulfites are still present, even when not deliberately added.
The following Australian wine makers claim to produce low or no sulfite wines or beers. This listing is for information purposes only, is not exhaustive, and should not be interpreted as a recommendation. Those interested should make inquiries of the manufacturer to verify these claims. There is also a product available that may reduce sulfite levels in wine without affecting the taste www.so2go.com.au
- Happs (Margaret River, Western Australia) Tel 08-8562 2598 www.happs.com.au
- Botobolar (Mudgee, New South Wales) Tel 02-6373 3840
- Macaw's Creek (Riverton, South Australia) Tel 08-8847 2237 www.macawcreekwines.com.au
- Hardy's "No added preservative wines" tel 1800 088 711 www.hardys.com.au
- Organic Wines Australia listings www.organicwine.com.au
- Coopers (Australia) Tel 08 8440 180 www.coopers.com.au
Select Organics Listing www.selectorganic.com.au
Sulfites are also used in some medications
Topical - some eye drops and creams
Oral medication - at the time of writing, no adverse reactions to sulfites have occurred from swallowed medication that might have been contaminated with sulfites.
Injectable medication - Adrenaline (epinephrine), isoprenaline, phenylephrine, dexamethasone and some other injectable corticosteroids, dopamine, local anaesthetics/dental anaesthetics containing adrenaline and aminoglycoside antibiotics are the most common potential sources of exposure. It should be noted that even in patients with serious sulfite sensitivity, the benefit of adrenaline is considered to outweigh any theoretical risk from sulfites in an emergency.
Management of sulfite sensitivity
Time - there is no evidence that sulfite sensitivity reduces with time
Avoidance - this is the mainstay of management. Commercial test strips to test food for the presence of sulfites are available in some other countries, but are not 100% reliable; these are not available in Australia at this time.
Switching off the sensitivity - there is no proven way of desensitisation or immunotherapy to reduce the severity of sulfite sensitivity.
Emergency action plan - those with relatively mild reactions like mild wheezing should carry their asthma puffers when eating away from home. Those with more serious reactions are managed along the same lines as anyone else with anaphylaxis, with provision of an ASCIA action plan for anaphylaxis, and training in the use of an adrenaline autoinjector (EpiPen or Anapen).
© ASCIA 2010
The Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional body of Clinical Immunologists and Allergists in Australia and New Zealand.
Postal address: PO Box 450 Balgowlah NSW Australia 2093
This document has been developed and peer reviewed by ASCIA members and is based on expert opinion and the available published literature at the time of review. Information contained in this document is not intended to replace medical advice and any questions regarding a medical diagnosis or treatment should be directed to a medical practitioner. The development of this document is not funded by any commercial sources and is not influenced by commercial organisations.
Content last updated June 2010