Dr. Gallagher is Emeritus Professor of Oral Maxillofacial Pathology at Boston University Henry M. Goldman School of Dental Medicine. He received his D.M.D. Degree from Tufts University School of Dental Medicine in 1972. After a general dental internship in what then was Boston City Hospital (now Boston Medical Center) and several years of private general dental practice, Dr. Gallagher completed a Doctor of Medical Sciences Degree (Experimental Pathology) at Harvard School of Dental Medicine in 1983. Dr. Gallagher served on the faculty at Harvard until his move to Boston University Goldman School of Dental Medicine in 2000. During his time at Harvard Dr. Gallagher helped to design the Problem-Based Learning curriculum in Oral Pathology at the dental school and participated in the problem-based learning courses in Histology and Pathology at Harvard Medical School. While at Harvard Dr. Gallagher received many teaching awards, and in 2006 he received the ADEA/Glaxo Smith Kline Sensodyne Excellence in Teaching Award from the American Dental Education Association.

Dr. Gallagher is a Fellow of the American Academy of Oral and Maxillofacial Pathology and a Diplomate of the American Board of Oral and Maxillofacial Pathology.