Douglas Barlow was born in 1894, at Gawler, South Australia. The second son of Mr AW Barlow, a retailer, he had three brothers and a sister. He was educated at the local school and then at Prince Alfred College, Adelaide. He had a brilliant scholastic career and was dux of the school in 1910, winning Elder and Longbottom scholarships, and top place in the State higher public school examination. The following year he started his medical studies at the University of Adelaide, and graduated with first-class honours in 1915.
His medical studies were then interrupted because he enlisted in the Australian Imperial Force, and served overseas. He was regimental medical officer 7 Battalion from 1916 to 1918, and was awarded the Military Cross at Ypres in 1917. After the War, he continued to serve in the citizen forces becoming Commanding Officer (CO) of 8 Hygiene Section, 1932-34; Assistant Director of Hygiene, 4 MD 1932-34 and CO of 6 Calvary Field Ambulance 1935. He was awarded the Efficiency Decoration and promoted to lieutenant-colonel in 1935. During the Second World War, he was a consultant to the Army.
He received his MD in 1922, after postgraduate work in England in 1920, and achieved recognition both as a pathologist and as an allergist. He was honorary pathologist and bacteriologist at the Adelaide Children's Hospital in 1922 and 1923, honorary clinical pathologist at Adelaide Hospital and demonstrator in pathology and bacteriology at the University of Adelaide from 1921 to 1923. From 1930, he became honorary medical officer at the asthma clinic at the Adelaide Children's Hospital, and honorary medical officer at the vaccine and asthma clinic at the Adelaide Hospital.
He was vice-president of the section of pathology and bacteriology of the Australian Medical Congress, Hobart in 1934. He was also a member of the committee for combating infantile paralysis, subsequently called the Crippled Children's Committee.
During the War, he started the first private pathology service in South Australia. He also began to focus more closely on allergy and was a foundation member of the Australian Society of Allergists. His wife Mora, a nurse and the daughter of Dr Charles Chewings, assisted him in manufacturing vaccines at home. He published a number of articles on research in asthma and hay fever, being one of the pioneers in this field in South Australia. After his untimely death in 1950, the late Dr Eugene McLachlan carried on his pathology practice.
His wife and their three children survived him – a daughter and son who became doctors, and a son who became an engineer.