FOOD ADDITIVES
Food additives are substances added to food at any stage of its production, processing , treatment or packaging, transportation or storage.They can be natural or synthetic. Natural food additives are more commonly implicated in anaphylactic reactions than synthetic ones.Synthetic food additives that have been reported to cause anaphylaxis are sulphites and benzoates.Suggestive situations include adverse reactions to multiple unrelated foods, circumstances where the food is tolerated at home but not when COMMERCIALLY prepared.SPecific IgE testing is useful to exclude IgE mediated allergy to the food components-for example if the patient ate a chicken burger at macdonalds and previously tolerated chicken it is unlikely to be the whole food component that is resposible for the adverse reaction. In this scenario or when a preservative reaction is suspected CAST testing is done. A CAST colourants and preservatives test may test for food colourants, tartrazine, Na – benzoate, K- Metabisulphite, Na- salicylate, MSG, K- Sorbate. These allergens are reported individually.A CAST ELISA is an in – vitro test that assesses the production of leukotrienes by the patients basophils following stimulation by the specific allergen under investigation.. Common preservatives and their sources include: Sulphites, MSG and Sodium Benzoate. Sulphites are widely found in alcoholic beverages includinf wine and beer fruit juices, jams, gravies , sauces, restaurant salads and fruit salads.Sodium benzoate is largely found in carbonated soft drinks,fruit juices, frozen dairy and cheese products. It is also found in mayonnaise. MSG is found in dried soup mixes, potato chips, crackers, diet food and in the restaurant industry to flavour savoury dishes.MSG is widely used in the restaurant industry and is implicated in Chinese REstaurant syndrome which is a complex of pain and numbness spreading down the arms, headaches, palpitaions, abdominal pain and flushing.Normally this follows ingestion of a high quantity of MSG. Symptoms occur within 30 minutes of the meal and may persist for up to 2 hours.
In conclusion food additives are used widely in the manufacture of food and although preservative reactions are thought to be uncommon (0.01 % – 2%), their prevalence may be greater in atopic individuals and children .Management invloves careful avoidance through checking food labels and elimination from the diet.