Schwartz advanced in academia, from the University of Arizona and the University of California, San Francisco to the Rutgers New Jersey Medical School, where in 1983 he became the first permanent head of dermatology, establishing a dermatology residency program in 1984. He is Professor and Dead of dermatology, Professor of Medicine, Professor of Pediatrics, and Professor of Preventive Medicine and Community Health at the Rutgers New Jersey Medical School. He is a Visiting Professor and Scholar of Public Affairs and Administration at the Rutgers School of Public Affairs and Administration. In 2014 Schwartz began serving on the Rutgers University Board of Trustees. Schwartz is also in his second term as President of the World Health Academy, serving from 2011 to 2012 and 2014 to present, and has been active on National Institutes of Health study sections since 2004. Schwartz has served as Faculty President of the Rutgers New Jersey Medical School in 1993 and 1995 and as Chairman of its Committee on Appointments and Promotions twice. He has been involved in many campus activities, including as Sigma Xi Scientific Research Society chapter president and Alpha Omega Alpha National Honor Society chapter councilor. He received the Faculty of the Year Award at the Rutgers New Jersey Medical School in 2002 and has been chosen as Top Doctor multiple times by New York Magazine, Inside Jersey, and Castle-Conolly Guide to Best Physicians. A two-time past president of the Dermatology Section of the New York Academy of Medicine, he has been elected to a third five-year term on the Board of Directors of the International Society of Dermatology. Schwartz has authored several books, most recently , a leading book on cutaneous oncology currently in its second edition. He has written or edited 10 monographs, and is the author of over 250 book chapters, 500 articles, and 200 other publications. Many of these are in the area of dermatologic oncology, where he has had a special interest in epidermal tumors, paraneoplastic syndromes, and Kaposi’s sarcoma. He has published more than 50 full articles on Kaposi’s sarcoma since 1978, including one of the first three reports of KS-AIDS in 1981. He was the first to describe many Kaposi's sarcoma morphologic variants. In 1978 he first described florid cutaneous papillomatosis. In 1981 he discovered and described acral acanthosis nigricans. In 1994 he devised the commonly-accepted classification for acanthosis nigricans.
Editorial activity
He has served as editor of the Acta Dermatovenerologica Alpina Panonica Adriatica, assistant editor of the Journal of the American Academy of Dermatology, associate editor of Cutis and Acta Dermatovenerologica Croatica, deputy editor of Mycoses, contributing editor of Dermatologic Surgery, and section editor of the Journal of Surgical Oncology. He is a member of the editorial boards of numerous journals, including American Family Physician, Anais Brasileiros de Dermatologia, International Journal of Dermatology, Indian Journal of Dermatology, Venereology and Leprology, Indian Journal of Dermatology, Giornale Italiano di Dermatologia e Venereologia, Postępy Dermatologii i Alergologii, Journal of the European Academy of Dermatology and Venereology, and Cesko-Slovenská Dermatologie.
In 1984, Schwartz married Camila Krysicka, a dermatologist and academic. Their son Edmund Janniger was an advisor to Polish Defence Minister Antoni Macierewicz for a short period of time in 2015.