Dawson was born in Truro, Nova Scotia, a grandson of John Barnhill Dickie and educated at Dalhousie University and McGill University. His research included studies on the transformation of pneumococci and on the biological variants of the streptococcus and other microorganisms. Dawson's studies on the nature and treatment of arthritis made him a recognized authority in this disorder. He was a pioneer in penicillin therapy, and was the first in the world to prepare it and use it in human disease. This included the successful treatment of bacterial endocarditis with penicillin, and the use of gold salts in the treatment of rheumatoid arthritis.