is a Hair Follicle Drug Test? When it comes to drug detection tests, hair follicle tests set a gold standard for accuracy. While a urinalysis is an excellent way to detect fairly recent drug use, the hair follicle test can test backward for the last 90 days giving highly accurate information about habitual drug use. You can find information to help pass a mouth swab drug test here. Thanks to its wide frame of test reference, hair follicle testing has become the standard for many corporations as well as being the standard for most government agencies. Hair follicle tests also prove useful due to their non-invasive nature and high difficulty to cheat.