How does hair folical hold thc?

Possibly months.: In “pharmacokinetics of cannabinoids” by mcgilveray ij it is stated “hair tests are more likely to detect regular than occasional marijuana use. One study found that 85% of daily users tested positive for marijuana, versus 52% of occasional smokers (1-5 times per week).

Long time: Hair and hair follicles may be positive for thc for at least 90 days -- even longer sometimes.