Allen was born and raised in Irvine, California. He completed his undergraduate training at University of California, San Diego as part of the combined-degree Medical Scholars Program with a major in Economics. After college, he completed a Fulbright Fellowship in Nicaragua before leaving California to attend Harvard Medical School where he earned his MD in 2014. His research interests include neuromodulation and expanding indications of functional neurosurgery and stereotactic radiosurgery, as well as functional neuroimaging for visualizing post-surgical changes in neural network connectivity.