I used a shampoo called 'Tommy Chong's urine luck, get clean shampoo' I don't care what anyone says, if you follow the directions you can and will defeat the hair test. I wasn't sure at first but I passed with flying colors and still have the paperwork to prove it!!!
Actually a Hair sample will show for about 90 days depending on how long you grow your hair it might even be longer. People say you can't beat a hair test but I did and have the paperwork to prove it. You just have to know what to get and use it exactly as the directions specify. I failed a urine test and came back and passed a hair test and they had to pay me for 9 days that I was fired and hire me back. I kept that job for another 3 years all because a hair test CAN be beat no matter what any one says.
Hair follicle is the most accurate of all testing since it goes back 90 days. You would have to be clean for at least 90 days in order to test clean. All drugs remain encased in the hair follicle.
It should take up to about a week but I don't advise anyone to try to fool someone, as traces may still be found
Until you shave your head completely...for 4-6 mos.