There is a whole other category of problems with food that the "experts" call food intolerance.  It is not life threatening like a food allergy.  It may be the tongue pain mentioned in two previous responses would fall in that category.

A true food allergy results in the production of antibodies (an immune system response).  When the response is strong it can result in aniphylactic shock and be life threatening. Folks with true food allergies carry epinephrine to counteract this response. I didn't read the NYT story (in spite of the useful link) but the 5% of adults with food allergies probably is this group.

From the point of view of nutritional scientists, the effect of allergies and intolerance is similar in that it limits the food choices of individuals.  Any limits such as these can contribute to a diet that does not provide the variety and balance that is recommended for good health. (Oops ... it is summer and I am not supposed to be teaching nutrition!)