I took 3 hits off a joint 6 weeks ago. Had not smoked prior to that in over 18 years. I have to take a hair follicle text next week. Was told I would probably be fine. Is that true? Would it be advisable to use a hair purifying treatment? Can they tell if you've used such a treatment?

Hair purify treatments don't work, in fact we used to laugh at people who thought they did, nothing on the outside of the hair effects the chemical make up in the hair.

But no, that little amount will not show up in a test.