Born in Greenwood, Mississippi, to Errol Ward Atkison and Mabel Blackwell Atkison, Allison graduated magna cum laude from the University of Mississippi Medical Center in 1971. After practicing primary care/internal medicine, in 1985 she returned to school to study cardiology, working in that field beginning in 1987. Allison transitioned in 1993 while living in Jackson, Mississippi, but lost her practice within a year of transition. She then moved to Phoenix, Arizona, for a position with CIGNA and currently serves as their chief of cardiology. Phoenix Magazine named Allison one of the "Top Doctors" in Phoenix for 2006, 2007, and 2008.