Allergen: Sulfur Dioxide and Sulphites

Sulphites are defined as sulfur dioxide and various inorganic sulfite salts which can release SO 2 under appropriate conditions (1). They can be found in a variety of foods, drinks and medicines, due to their antioxidant properties, which prevent oxidation and browning of foods, and antimicrobial properties, acting as preservatives (1, 2, 3).
In this article you can learn more about adverse reactions to sulfites, what foods you can find sulfur dioxide and sulfites in and how to identify them on labeling.

The prevalence of sulfite sensitivity in the general population is unknown, but it appears to be more common in asthmatics, particularly those who have nasal polyps and are sensitive to acetylsalicylic acid (aspirin), which may precipitate asthma attacks.

Adverse reactions to sulfites can occur by ingestion or inhalation and are not yet clearly documented. However, three possible mechanisms are considered:
a) IgE-mediated reaction, which was difficult to demonstrate by scientific studies and was considered unlikely given the nature of the molecule (it is not a protein);
b) cholinergic response (from the parasympathetic nervous system) induced by sulfites;
c) low levels of the sulfite oxidase enzyme. (1)

These reactions, although not mediated by true allergy mechanisms, manifest themselves clinically in the same way. Most reactions to sulfites are characterized by bronchospasm, occasionally severe, which may occur within minutes of ingestion. Other symptoms can range from headache, red skin, hives, wheals, rhinitis, nausea, vomiting, abdominal cramping, diarrhea, chest tightness, hypotension, angioedema, and anaphylaxis. (1, 2, 3)

The maximum levels of sulfites that can be added to different foods and beverages are legally defined, and an SO2 content not exceeding 10mg/kg or 10mg/L is considered not present and, in concentrations greater than 10mg/kg or 10 mg/L of SO2 is subject to mandatory labeling in the European Union. This limit was determined based on the ability of analytical methods to detect sulfites in foods and beverages, but the minimum amount of sulfites capable of triggering a reaction in a sensitive person is unknown (1).

Products that contain or may contain sulfur dioxide or sulfites: (4,5,6,7)


How to identify Sulfur Dioxide and Sulphites on labeling: (5, 7)

At Fidu we do not use artificial additives and therefore our products do not contain sulfur dioxide or sulfites, making them safe for those who are hypersensitive to these substances.

Learn more about our products here.

IMPORTANT NOTE : The content of this article is merely informative and should not replace medical advice. If you suspect that you suffer from this type of allergy, you should seek medical advice.
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(1) NDA. (2016). Scientific Opinion on the evaluation of allergenic foods and food ingredients for labeling purposes. EFSA Journal, 12(11).
(2) Coimbra, A., et al. (SPAIC). Patient Education Manual: Allergens and Food Additives.
(3) SPAIC Food Allergy Interest Group, 2017. Food Allergy: Concepts, Advice and Precautions, 1st Edition. Lisbon: Portuguese Society of Allergology and Clinical Immunology with support from Thermo Fisher.
(4) ASAE. (2017). Food Allergens. In Risks and Foods (Vol. 13).
(5) Regulation (EU) No. 1129/2011 of 11 November 2011 of the European Commission.
(6) Pádua, I., Barros, R., Moreira, P., & Moreira, A. (2016). Food allergy in catering. Lisbon: National Program for the Promotion of Healthy Eating, Directorate-General for Health.
(7) Regulation (EC) N. 1333/2008 of 16 December 2008 of the European Parliament and of the Council of the European Union.