My grandson started having periodic very high fevers when he was about two years old. Temps went dangerously high and he was hospitalized numerous times. His parents took him to many different hospitals and tests showed nothing irregular. Finally, after nearly a year of continuous tests and hospitalizations they took him to Mayo in Rochester, MN. Within hours a diagnosis was made.....PFAPA. It is an autoinflammatory disease, with at that time, no known cause. It almost entirely occurs in children, and though it happens, it is rare in adults. My grandson was prescribed prednisone, which he is given immediately when his temp starts to rise. Works promptly and cancels out the temperature spike. He is now seven years old and though he still has an occasional episode, they are much less frequent. Reports are that most children outgrow it eventually. In any case, PFAPA certainly may have nothing to do with your temperature spikes, but thought I'd just share my grandson's story with you and perhaps you might want to research PFAPA a bit and and also some of the other reasons that could cause temperature to rise periodically.