Hair folicle testing is the most thorough of all the tests done. If the hair is one year old then it will contain the history of your drug use for one year. The hair test is also used to weed out individuals who have genetic predispositions toward diabetes, heart disease, cancer etc., you get the idea. It is an expensive test and generally only used by corporations who perform 'sensitive' services for the military/industrial complex. You would have to remove EVERY hair on your body as well as your finger and toenails to not be able to participate and if you did that they would automatically reject you.