Sulfites are used in the pharmaceutical and food industry for their antioxidizing and antibacterial properties. SO2: sulfurous anhydride. Na2SO3: sodium sulfite. NaHSO3: sodium bisulfite. Na2S2O5: sodium metabisulfite. K2S2O5: potassium metabisulfite.
< 2% in the general population.
4 to 8% of asthmatics are sulfites sensitive.
1.7% of positive sodium metabisulfite patch-tests in patients with eczematous dermatitis.
The majority of sulfite reactions are dietary; 3% of total reactions are attributed to drugs.
Risk factors
Aspirin intolerance?
Steroid dependent asthma.
Clinical manifestations
(reported with: novocaine, lidocaine, gentamicin, metoclopramide, vitamin B injection preparations, doxycycline)
Anaphylactic shock.
Asthma (steroid-dependent chronic asthma).
Urticaria, angioedema, periorbital edema, contact dermatitis.
Laryngeal edema, nasal pruritus, rhinorrhea.
Mode of exposure
Food: preservative in dried food (e.g. fish), bleaching agent in codfish filets, dried fruits, fresh grapes, candies, vegetables, shrimps, wine, beer, cider, fruit and vegetable juice.
Drug: at least 1000 sulfite-containing drugs in USA (aminoglycosides, local anesthetics with epinephrine, corticosteroids, antifungal creams).
Diagnostic methods
Cutaneous testing.
  • Skin-prick tests (1 to 10 mg/ml), intradermal skin-tests (5 mg/ml), delayed skin-tests with sulfite solution 2% are usually negative.
  • Patch-tests with sodium metabisulfite 1% in petrolatum are used in the diagnosis of contact allergy.
Challenge tests.
  • Oral challenge tests: 5,10,25,50,100 mg dissolved in 20 ml of 0.5% citric acid positive in 20% of steroid-dependent asthmatic children.
  • Inhalation challenge tests.
  • Subcutaneous challenge tests (do not exceed 10 mg): not always positive in sulfite-sensitive individuals.
Several hypotheses:
  • IgE-mediated hypersensitivity (positive skin-tests, positive transfer-tests, no specific IgE found)
  • Inhalation of sulfur dioxide (bronchoconstriction)
  • Direct nervous stimulation by SO2
  • Direct membrane toxicity
  • Sulfite oxidase deficiency
  • Delayed contact sensitivity in contact eczema.
Cyanocobalamin is effective in preventing clinical sulfite reactions.
Avoid use:
  • Foods: easy if the presence of sulfites is indicated on the package label. If not, a detection band can be used, but false negative results are frequent.
  • Drugs: see the drug listing, or use detection band.


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  3. Vena G.A, Foti C, Angelini G, "Sulfite contact allergy", Contact Dermatitis, 1994; 31 (3): 172-5
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  5. Sanz J, Martorell A, Torro I, Carlos-Cerda J, Alvarez V, "Intolerance to sodium metabisulfite in children with steroid-dependent asthma", J. Investig. Allergol. Clin. Immunol, 1992; 2 (1): 36-8
  6. Smolinske S.C " Review of parenteral sulfite reactions", J. Toxicol. Clin. Toxicol., 1992; 30 (4): 597-606

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.