Body hair has a similar rate of growth as head hair, with a range of between approximately 0.9 and 1.1cm per month, but it has a different pattern of growth and resting phases. It has been estimated that body hair has a much higher proportion, approximately 40% - 60%, in the resting phase compared to only 10% - 15% for head hair.
As a consequence body hair samples are not divided into sections for analysis and any use of or exposure to a detected drug may have been in the weeks prior to the sample collection or many months earlier than this.