Between 10% and 20% of consumers claim to have food allergies, but the real number may only be half this, according to a study published in the German journalDeutsches Ärzteblatt International(International German Medical Journal).

The study, conducted at Wurzburg University, examined 419 people who had been referred to a clinic for a suspected food allergy. Judging by the presence or absence of the antibody associated with allergic responses, just over half of the subjects had true food allergies.

Suspected food allergies are driving the growth of foods with “free-from” claims. The growth has been more than 100% in the U.S. since 2004, according to Business Insights. It also is the impetus behind an increasing number of product recalls, when trace amounts of lactose, gluten or other substances are suspected of infiltrating products that do not declare them on their labels. Allergen-related recalls by the Food and Drug Administration have more than quadrupled since 1998.