McIntosh was born and raised in Lanarkshire, Scotland. Having begun to write at age seven, she credits the author who inspired her to write as "probably Angus MacVicar!" She lived and worked in Glasgow for many years before moving to the west coast of Scotland. Prior to making her mark as an author, she worked as "a librarian, a receptionist for an alternative therapy centre, taught geology and palaeontology, [and] tutored for the Open University."