How long does MDMA stay in your system for a hair drug test??

It's laid down in the protein that makes up the hair itself during the period it's in your bloodstream- Once there, the hair shaft saves it as a record- It would take about a week or 2 for the hair to grow out enough for you to cut it- If you shaved yourself bald, right to the scalp, two weeks after the exposure, that would be the shortest time I could see. If you do not shave your head, though, the hair will maintain that MDMA level until it is cut.

How long does MDMA stay in your system for a hair drug test??

The whole point is, that a hair drug test can be done MONTHS after a drug is out of your system, THAT is why they use it.

Hair is dead from the moment it leaves the follicle, but retains toxins, poisons etc for months afterwards, thats how forensic can tell if someone has been poisoned even years later.

Hair grows approx 1/2" per month, so work out how many months you have to wait to cut the hair to get rid of any eveidence.

How long does MDMA stay in your system for a hair drug test??

The user could try using oxidizers like bleach to attack the chemical structure, or UV light to try to break it up, but if they use some test like FTIR they may get a IR absorbance at MDMA's characteristic frequency - it could be difficult to defeat the test. The user could try to get the MDMA to bond with some other chemical and change its frequency response, but this might be difficult to do when it's still on the head.

Best thing: don't use MDMA