How long does thc stay in hair?

Depends..: Chronic use may show positive results for months. It depends also on the length/amount of hair tested and the nature of the test being used. Check this link for more details. http://www.ncbi.nlm.nih.gov/pmc/articles/pmc2274831/.

It may be detected: In hair follicles for 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).

Up to 3 months.: If a regular user, it can still be detected in 3 months.