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.
Steroid dependent asthma.
(reported with: novocaine, lidocaine, gentamicin, metoclopramide, vitamin B injection preparations, doxycycline)
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).
- 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.
- 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.
- 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.
- 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.