Both immunity to scarlet fever and immunity to diphtheria as measured by cutaneous reactions vary from time to time. We have observed the frequency with which negative reactions become positive over a period of years in several groups of children. This study constitutes a continuation of our previous reports on factors which affect cutaneous reactions.1
Our purpose was to examine normal variations of cutaneous reactions, uninfluenced by the immunity which may be produced by disease or by artificial immunization. At intervals of one or two years the entire populations of several orphanages were tested with Dick and with Schick toxins. All of the children who had positive reactions were subsequently given injections of immunizing agents and were therefore no longer included in the study. Children whose original tests gave negative results were retested from year to year, and the spontaneous reversals2 in this series of children are here recorded.