IN A SERIES of scattered papers based on observations covering three decades and intensified in the past ten years, Stokes and his associates have outlined a concept of infection allergy which, when applied to the inflammatory dermatoses as an explanation of onsets, relapse and noncure, they have called the virus-pyogen sensitization sequence. The effort is comparable to the of Milian1 in outlining the biotropic concept of the activation of infections by drugs with the production of certain types of so-called drug eruptions. To this related field certain observational contributions have been made, particularly in the matter of arsenical exfoliative dermatitis, by Stokes and Cathcart2 and Stokes and Kulchar.3 Stokes and Callaway4 pointed out the types of pyogenic relapse that seemed to follow clinical virus infections, including the epizootic seasonal type, often after a lag, or refractory period, of seven to eleven days, following which the