Hair drug testing requires a small sample of hair that is collected under direct supervision without any invasion of privacy. During a hair collection, the collector cuts approximately 100-120 strands of hair from the crown of the donor’s head. The hair is cut as close to the scalp as possible, so only the strands of hair above the scalp are tested and not the actual hair follicle (the pocket below the scalp from which the hair strand grows). This makes hair testing a tamper-resistant, observed drug screening method.