In the scientific aspects of immunology, the pace of advance has been almost overwhelming, but with some notable exceptions, clinical benefits have been slow. For those who are interested in allergy, the situation has been somewhat different. Here, the scientific aspects have lagged sadly behind other branches of immunology. There has, however, been a recent explosion of knowledge, which began with the discovery of immunoglobulin E, and a curious situation has come to light. The speculations of the older allergists, which had often been derided as mere inventions, now appear to be largely...