We have read the interesting review on the clinical effects of sulphite additives recently published in the journal [1]. Sulphite hypersensitivity, particularly when manifesting mainly with cutaneous symptoms, remains a dark area of diagnosis where work-up and outcomes are frequently unclear. In this respect, here we describe a case that may help in the diagnostic work-up of patients claiming sulphite allergy.A 56-year-old non-smoking, non-asthmatic mechanic with no history of allergy, living in a vineyard area on the Mediterranean coast reported that 3 years before he had started to suffer bilateral ear pruritus, conjunctival redness, facial rash, lip angioedema and sometimes generalized urticaria after drinking local wines purchased directly from local cellars. As a consequence, he switched to bottled brands, but the process continued, extending later to some processed meats, although he was able to eat nonprocessed beef and pork. Baseline spirometry was normal, and bronchodilator test was negative. Standard prick tests with inhalant allergens and latex were negative. An extended battery of 34 food skin tests, including different kinds of grapes, as well as 18 spices used in food industry, were negative. A skin prick test with 10 mg/mL sodium metabisulphite in saline proved negative. A double-blind placebo-controlled sulphite provocation test with sodium metabisulphite showed ear and facial itching, neck redness and two large retroauricular hives 25 mm in diameter after the 10 mg metabisulphite dose. Spirometry at baseline and at the end of the tests was unchanged. A basophil activation test (BAT), performed using 5.21 and 20.8 mg/ mL of sodium metabisulphite, yielded a strongly positive result (stimulation index: 8.8). The patient was therefore diagnosed of sulphite sensitivity and instructed to avoid eating manufactured foods, which could contain sulphites as additives, as well as wine. After 6 months, he has not suffered further episodes of itching or urticaria.Although immediate cutaneous sulphite hypersensitivity has long been known [2, 3], it is rare to find proven cases in daily practice, with most patients suffering chronic urticaria and reporting inconsistent and varying symptoms that are invariably attributed to industrial foods or 'additives' and which can seldom or never be proved with objective tests [4]. Nevertheless, some cases of sulphite sensitivity leading to recurrent urticaria or anaphylaxis may occur that merit investigation and accurate diagnosis [3, 5]. The BAT and a placebo-controlled challenge test can help to identify sulphites as the culprit substance in some of these patients and allow them to avoid potentially harmful foods by simply reading labels or asking about composition.
References1 Vally H, Misso NLA, Madan V. Clinical effects of sulphite additives.
