(HealthDay)—Some bakery products sold as free of cow's milk may not be safe for those with milk allergies because they still contain milk protein, according to research published online Feb. 4 in Allergy.

Valérie Trendelenburg, of the Charité Universitätsmedizin in Berlin, and colleagues sent questionnaires to 200 parents who had a child with a food allergy and interviewed staff from 50 bakeries. Cow's milk protein levels in bakery products described as "cow's milk free" were measured using enzyme-linked immunosorbent assays.

The researchers found, based on 104 returned questionnaires, that 25 percent of the children experienced an allergic reaction caused by non-prepacked food from baker's shops, and 20 percent had an allergic reaction to food products from ice cream parlors. Among bakery staff, 60 percent reported serving customers with food allergies at least once a month and 24 percent, at least once a week. The majority of staff (84 percent) felt capable of advising consumers with food allergies about safe product choices. Of 73 products sold as "cow's milk free" in 44 baker's shops, cow's milk protein was detected in 43 percent; 21 percent of the products contained more than 3 mg of cow's per serving.

"Cow's milk was detected in many bakery products sold as 'cow's milk free' posing a potential risk for food allergic customers, especially those reacting to low amounts of 's milk," the authors write.