Hair Testing (Hair Follicle Screening):
Hair testing is considered accurate and at average can go back 90 days, As hair grows out, any drugs used are encased in the hair shaft. Longer hair can reveal an individual's drug history spanning a longer period than shorter hair. Human hair grows an average of 0.5 inches/month, which corresponds to 30 days of possible drug testing for approximately every half-inch. Testing laboratories generally require between 0.5 and 1.5 inches for testing. This represents approximately 30 to 90 days of drug use. But is not limited to the 90 days. Hair tests can go back up to years prior if the person has the hair length that is required for example if someone would like the test to go back a year it would require 6inches of head hair, if they would like to go back 2 years it would require 12inches of head hair and so on (this testing is available at an extra cost). The standard for hair 1.5 inches or longer is 80 strands or 120 if only 0.5 inches is going to be tested. As it is by picogram weight that the hair is uniformly tested. Some people attempt to circumvent this through shaving their heads. This does not usually work. In the absence of the required amount of hair on the scalp, body hair can be used as an acceptable substitute in the order of face, chest, arm pit, and on some occasions the police use leg hair that has a slower growth rate. It costs more than urine testing, and one must have a lab for results. Hair testing is becoming more reliable as technology advances, and there is no known way to adulterate a hair specimen in order to falsify the results of the test, despite what some retailers advertise.
Radioimmunoassay of hair is a revolutionary new drug screening process that can determine an individual’s drug history, not just the amount of drugs present in the body at the time of testing, but over a period of months or even years.