Like many a guide to the medically perplexed, this text proposes that your complex health problems may be due to a single cause--in this case, allergy to substances in air, water, or food. The symptoms are not restricted to hives or asthma either. The key to mental symptoms such as depression, hyperactivity, psychosis, and learning disabilities--as well as to physical symptoms ranging from arthritis to vasculitis--may lie in the plastic wrap on the lamb chops, dust in the mattress, fumes from the wallpaper paste, insecticide sprayed on the bananas. With the usual caution to seek medical supervision--preferably from a new genre of specialists called clinical ecologists--the reader is counseled to test for sensitivity by undergoing an initial few days' fast (drinking pure spring water only). This is to be followed by a rotary diet in which single foods are introduced at each meal over a course of a week, with the cycle repeated to establish reliability. As usual, there are ample case histories of the horror-but-hope variety: the psychotic restored to normally, the emaciated to health, the irascible to sweet-temperedness. Virtually nothing is said about cause and effect in physiological terms, about the immune system, genetic factors, or changes in development, and even less about the incidence and prevalence of allergies. So beware. The good news is that there's a lot of useful, practical information here even if you're not a candidate for the rotary diet: household hints on removing stains and general cleaning, wholesome simple recipes, lists of foods and food families (if you're allergic to gin you may be allergic to pine nuts too), guides to furnishing a house, selecting clothing, etc. With selectivity, anyone who has discovered the joys of wearing pure cotton and generally would prefer a plastic-free existence can profit.