Those vague statements on food products, really legal disclaimers, such as, “may contain nuts,” can leave people who have food allergies wondering if something is safe to eat or not.

So British researchers recruited over 400 people for a study in which they ate small portions of the food they were allergic to and then had their reactions monitored.

The researchers analyzed people's responses to the levels of five of the most common food allergens — peanuts, hazelnuts, shrimp, fish, and celery, a frequent cause of food allergy in European countries.

Almost any food can cause an allergic reaction, but there are eight foods that account for 90 percent of all allergic reactions in the US.

“What we wanted was to find a level of allergen which would produce a reaction in the most sensitive ten percent of people. This sort of data can then be used to apply a consistent level of warning to food products,” said Professor Clare Mills of the University of Manchester who led the study.

The most sensitive or highly allergic people reacted to 1.6 to 10.1 mg (between about one-eighth to two teaspoons) of hazelnuts, peanuts, and celery, and to 27.3 mg of fish. However, it took 2.5 grams of cooked shrimp to produce a response. Raw shrimp weren’t studied and may have a different effect.

Food allergies are on the rise in the United States. The Centers for Disease Control and Prevention reports that food allergies increased among children by approximately 50 percent between 1997 and 2011. About nine million American adults and six million children have food allergies.

Almost any food can cause an allergic reaction, but there are eight foods that account for 90 percent of all allergic reactions in the US: peanuts, tree nuts, eggs, milk, wheat, soy, fish, and shellfish.

According to the Food Allergen Labeling and Consumer Protection Act of 2004, these eight allergens must be clearly stated in simple terms on food products, whether listed in the ingredients or as an allergen statement. But then there are those products that may contain traces of an allergen, such as the potential presence of peanuts in foods made in a factory where peanuts are used in other foods. These precautionary labels are not regulated, and they are not consistent.

Mills and her team hope the findings from this study will better inform those who suffer from food allergies about the doses that could trigger a response, as well as provide better food product labeling. “What we’d like to see are warnings which tell people with allergies to avoid certain products completely [and which] just apply to those who are most sensitive,” said Mills.

The study was published in the Journal of Allergy, Asthma and Clinical Immunology.