Hair testing can reveal drug use within a larger time frame than urine testing because urine is excreted relatively quickly from the body.
Hair grows at the rate of about a half-inch per month.
Psychemedics Corporation, the largest hair testing company in the U.S., sponsors pilot programs in private schools. Psychemedics recently sponsored free hair testing for a year to two private schools in New Orleans De la Salle High School and St. Augustine High School. At De la Salle, only 28 of the 870 students tested positive with three months' notice of the test. Test results were released to parents, and students who tested positive were referred to drug counseling. When the students who tested positive were retested, only three tested positive.