Drug testing if a person do not use drugs how cam he test positive on hair drug test

For example, certain medications may influence the results of the test.

Drug test can show the presence of illicit or prescription drugs on hair samples, although the person has not used these drugs.

Some of false positive drug use is because of this medications: antihistamines, decongestants, antibiotics, antidepressants, analgesics and antipsychotics.