Since hair is not living tissue, it is unaffected by bodily processes and functions. Your body can’t clean the drugs out of your hair. No shampoo can remove it, either. Traces of the drug are built into each strand of hair, similar to how food you eat is digested and becomes part of your muscles, blood, fatty tissue, etc. Trying to wash the drugs out of your hair would be like trying to clean your blood/urine of drugs by taking a long, hot, soapy shower.
Hair tests are 99% accurate, can detect drugs for up to two years after you’ve used them (depending on the length of your hair) and are virtually impossible to cheat. I’m sorry to say that, if you have to take a hair test for a job, there is no solution besides finding another job that will not ask for a hair test. Maybe you can reapply to that other job in two years time.