The five foods they considered were peanut, hazelnut, celery, fish and shrimp. Between 1.6 and 10.1 milligrams of hazelnut, peanut and celery protein produced a reaction in the most sensitive 10 percent of those studied.
For fish, it was higher at 27.3 milligrams and for shrimp, a significantly higher 2.5 grams of cooked protein produced a reaction though the researchers did not study raw shrimp which may have a different effect.
"What we wanted was to find a level of allergen which would only produce a reaction in the most sensitive ten percent of people," said lead researcher professor Clare Mills University of Manchester in Britain.
"This sort of data can then be used to apply a consistent level of warning to food products. What we would like to see are warnings which tell people with allergies to avoid certain products completely or just apply to those who are most sensitive," Mills explained.
The researchers analysed data from 436 people across Europe who had allergies to peanut, hazelnut, celery, fish or shrimp. They were then given small doses of the food they were allergic to and their reactions were monitored. The study appeared in the Journal of Allergy and Clinical Immunology.