Most of the studies in which food allergy is clinically proven report that between 1 in 100 and 1 in 20 people overall have a food allergy. Individuals with food allergy develop symptoms by eating foods that for the vast majority of the population are part of a healthy diet.

To help allergic individuals avoid foods to which they are sensitive, allergen labelling rules in various countries require food manufacturers to declare specified allergens on labels whenever they are deliberately used in a product. This requirement is irrespective of whether the allergens are present in amounts that may pose a risk to people allergic to those ingredients.

However, labelling rules do not generally cover the small amounts of allergens that may be present in many products due to cross-contamination during the production process. If food manufacturers consider that there is a risk of cross-contamination with allergens in their products they will often include an allergen advisory warning on the label, for example “May Contain Peanuts” or “Manufactured in the same building as foods containing soy”. However, the overuse of such labels presents allergic consumers with a dilemma. They can either accept decreased food choices or hope that, if present, the level of allergen in the food is insufficient to trigger a reaction. But they are taking a risk, as recent studies pointed out that 5 to 10 % of the “may contain” products indeed contained the allergen to which the warning referred.

Read EuroPrevall report on What amounts of foods may trigger food allergy symptoms?

Reference

R. W .R. Crevel, B. K. Ballmer-Weber, T. Holzhauser, J. O'B. Hourihane, A. C. Knulst, A. R. Mackie, F. Timmermans, S. L. Taylor (2008). 
Thresholds for food allergens and their value to different stakeholders. 
Allergy 63, 597-609.

More information
EuroPrevall website
InformAll database - for detailed information on the foods, which may cause allergic reactions.