The Australasian Society of Clinical Immunology and Allergy

Keywords -sulfur allergy, sulfite allergy, sulfites, sulfonamide allergy, drug allergy, antibiotic allergy

Note: This document uses spelling according to the Australian Therapeutic Goods Administration "Approved terminology for medicines" (1999) in which the terms sulfur, sulfite, sulfate, and sulfonamide replace sulphur, sulphite, sulphate and sulphonamide.

Being told that one is "sulfur allergic" commonly causes confusion, as many people wrongly assume that they will be allergic to multiple sulfur-containing medicines or sulfite preservatives.  It is important to know that sulfur is an important building block of life, and that allergic reactions to sulfonamide (sometimes called "sulfur") antibiotics do not increase the likelihood that a person will also be allergic to sulfur powder, sulfite preservatives, or non-antibiotic sulfonamide medicines like some pain killers or diuretics ("water tablets").

Sulfonamide antibiotic allergy

Sulfonamide antibiotics can cause allergic reactions, ranging from mild to severe rashes through to anaphylaxis (allergic shock). If you are allergic to one sulfonamide antibiotic, you should avoid other sulfonamide antibiotics. Sulfonamide antibiotics available on prescription in Australia include:

• Sulfamethoxazole used in combination with trimethoprim, available as Bactrim, Resprim or Septrin.
• Less commonly used sulfonamide antibiotics include Sulfadiazine (tablets, injection or cream), Sulfadoxine (for malaria), and Sulfacetamide antibiotic eye drops.
• Sulfasalazine (Salazopyrin, Pyralin), used in inflammatory bowel disease or arthritis, is a combination sulfapyridine (a sulfonamide antibiotic) and a salicylate.

If you have had an allergic reaction to Bactrim, Resprim or Septrin, there is no way of knowing whether the allergy was to sulfamethoxazole or to trimethoprim, therefore you should avoid trimethoprim (Alprim, Triprim) as well as sulfonamide antibiotics.

There are other types of sulfur-containing substances

Elemental sulfur powder. This is commonly used in gardening, and while irritation may occur from skin contact or inhalation, allergy has not been described.

Sulfates. Some injectable drugs are sulfate compounds, for example heparin sulfate, dextran sulfate, morphine sulfate. The sulfates in soaps (such as sodium lauryl sulfate) are strong detergents and can irritate the skin or eyes, however sulfate itself does not cause allergic reactions. It is usually safe to use a sulfate when a person has a sulfonamide or a sulfite allergy.

Sulfite preservatives. Commonly known as sulfur dioxide and metabisulfites, preservative numbers 220-228, sulfites are a group of compounds used to preserve flavour and colour and within food, inhibit bacterial growth, reduce spoilage, stop fresh food from spotting and turning brown and help preserve medication and increase shelf life. They are found most often found in wine, dried fruit, dried vegetables and sometimes sausages and salads. They can also occur naturally in low concentrations.  Sulfites can cause allergy-like reactions (intolerances), most commonly asthma symptoms in those with underlying asthma, sometimes hay fever-like reactions, occasionally urticaria (hives) and very rarely, anaphylaxis (allergic shock). Additional information on sulfite sensitivity is provided in a separate information article. There is no relationship between sulfite sensitivity and sulfonamide antibiotic allergy.

Non-antibiotic sulfonamide medicines. Some medicines contain sulfonamide molecules unrelated to sulfonamide antibiotics (eg. some fluid tablets, diabetes tablets, some pain killers/arthritis tablets).
* It is important to note that these medicines do not need to be avoided by people because they are allergic to sulfonamide antibiotics; the allergy rarely if ever "crosses over".

Confirming the diagnosis

Skin allergy testing may be useful in some cases of suspected sulfonamide antibiotic allergy, but is not considered useful for assessing adverse reactions to sulfite preservatives. Skin testing may assist in distinguishing between allergic reactions to sulfonamide antibiotics and those to trimethoprim in individuals who have reacted to combination antibiotics such as Bactrim, Septrin or Resprim. These procedures are normally conducted by allergy/immunology specialists.

Management

The mainstay of management is avoidance. Those allergic to one sulfonamide antibiotic, should avoid all sulfonamide antibiotics. Since these antibiotics are not normally used in an emergency, wearing a MedicAlert bracelet is not routinely recommended. "Desensitisation" protocols to switch off antibiotic allergy temporarily are available should a sulfonamide antibiotic be the only suitable drug to use, but this is not possible in all cases of sulfonamide allergy, and this process does not work for sulfite preservative sensitivity.

© ASCIA 2007
The Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional body of Allergists and Clinical Immunologists in Australia and New Zealand.

Website: www.allergy.org.au

Disclaimer:

ASCIA Education Resources (AER) information bulletins have been peer reviewed by
ASCIA members and represent the available published literature at the time of review.

It is important to note that information contained in this bulletin is not intended to replace professional medical
advice. Any questions regarding a medical diagnosis or treatment should be directed to a medical practitioner.

References

1. Strom, B.L., et al., Absence of cross-reactivity between sulfonamide antibiotics and sulfonamide nonantibiotics. N Engl J Med, 2003. 349(17): p. 1628-35.
2. Montanaro, A., Sulfonamide Allergy, in Drug Hypersensitivity. 1998, W. B. Saunders Company. p. 843-849.
3. Johnson, K.K., et al., Sulfonamide cross-reactivity: fact or fiction? Ann Pharmacother, 2005. 39(2): p. 290-301.
4. Hemstreet, B.A. and R.L. Page, Sulfonamide allergies and outcomes related to use of potentially cross-reactive drugs in hospitalized patients. Pharmacotherapy, 2006. 26(4): p. 551-7.
5. Brackett, C.C., H. Singh, and J.H. Block, Likelihood and mechanisms of cross-allergenicity between sulfonamide antibiotics and other drugs containing a sulfonamide functional group. Pharmacotherapy, 2004. 24(7): p. 856-70.

Content Lat updated 1 January 2007