Now my head hurts, lol!
I worked at a place that required hair follicle tests, you can buy a shampoo at GNC that will beat it . Worked for me hahahaAfter recalls from layoffs, my employer/facility did drug testing via hair samples. IIRC, it could be found if taken even thirty days prior. Some miscreants shaved their heads and private parts to try and bypass the test. They were told to go home and come back when they had hair and their UC was cut off.
I laughed so much at this, it happened at my neighbors house with his new pup had to hose off the robo vac thank god he had a tiled floor & not carpet.