Individual hypersusceptibility to chemical substances is a well-known phenomenon in toxicology and pharmacology.' The role of this phenomenon in pathological reactions to common foods, however, is imperfectly understood. If suitable measuring techniques were available, this field should lend itself to a study of biological variation in humans. Problems arising from individual variations in tolerance for common foods have been recognized since antiquity.' Progress in understanding and controlling these problems has been painfully slow. A major portion of this difficulty has been due to the fact that man has only a limited number of physiological mechanisms for adaptation to his constantly changing environment so that the same adaptation reactions occur in response to a broad variety of stimuli. It is very difficult to keep a subject isolated from all extraneous stimuli in order to test the effect of a single factor. Another unsolved problem is to determine the boundary between a normal adaptive response and a pathological reaction. Even when abnormal reactions are obvious, it is very difficult to establish a causal relationship with a single factor. This laboratory has been engaged in chemical and physiological studies designed to aid in both understanding and diagnosing pathological responses to foods.Two broad categories of abnormal responses to unspoiled foods have been studied. The earliest group to be classified was that labelled as "allergic."3 Shortly afterward, responses falling into the category of "inherited metabolic defects"' were recognized. Disentangling the two categories is difficult in many cases. Indeed, Godlowski5 presents arguments for regarding all allergic responses as due to inherited metabolic defects. While this is a theoretical possibility, it seems wise at the present time to reserve this category for cases in which the enzymatic abnormality causing the pathological response can be identified with precision. Examples have been described by Mountain6 in which hereditary deficiencies in enzyme systems of erythrocytes produce hypersusceptibility to a large number of commonly used chemicals. A comprehensive study of metabolic errors has been prepared under the editorship of Stanbury, Wyngaarden and Fredrickson.'One method proposed for the diagnosis of food allergy is that of A. F. Coca.s His procedure requires a systematic recording of the pulse acceleration of an individual upon exposure to suspected foods or inhalants. His conclusion that all allergic reactions are accompanied by pulse accelerations amounts to a definition of food and inhalant allergy in terms of pulse response. It is certainly conceivable, however, that other responses might occur independently of pulse accelerations. Corwin, Hamburger and Dukes-Dobosy have examined Coca's data and have found that the changes in heart rates of the individuals whom he studied have magnitudes that satisfy the requirements of statistical significance. This suggests an abnormal reactivity of the autonomic nervous systems of these individuals ...
