Allergies have been on the increase for years and now six percent of children and three percent of adults suffer from food allergies.
There's no one reason for the increase, says Stephan Meller, an allergist and senior doctor at Dusseldorf University Clinic.
Contributors include the environment, food and habits that might mean a person typically avoids something.
Since 2008, the German Allergy and Asthma Association (DAAB) has been marking the illness - which affects hundreds of thousands of people and for which there is no cure - with a food allergy awareness day on June 21.
"The only thing that works is for the patient to know what he or she is allergic to and to avoid that foodstuff," says DAAB's Sonja Laemmel.
That means the ingredient that causes the reaction must be clearly marked on packaging or on labels for loose products in restaurants and bakeries, which is not always the case.
In Germany, stricter rules have been in force since December: ingredients that could potentially cause a reaction have to be written in bold or underlined on packaging labels.
That includes gluten, milk, eggs, fish, nuts, soya, celery and sulfite.
There's still a problem with products that are sold loose however: sausages from the butcher and rolls from the baker should also be labelled according to the December regulation, but this hasn't necessarily been happening.
Customers often have to double-check.
"It's a catastrophe for people who are allergic," says Andrea Wallrafen, the director of DAAB.
Allergic reactions to food can be confusingly diverse. They range from itching, redness and welts to sneezing fits and runny noses, coughing and breathlessness as well as diarrhoea, vomiting and nausea.
The worst form of allergic reaction is anaphylactic shock, which can be fatal.
People's allergies vary according to age: for babies, cow's milk and chicken's eggs are the most common culprit.