A simple way to test for whether or not an individual has been using drugs is to administer a hair drug test. This is one of the best ways, in fact, to detect drug usage in a person because it is fairly non-evasive and is always fool proof, and takes place using a part of the body that everyone has. Hair does not necessarily need to be taken from the head; rather, it can be taken from anywhere on the body.

The science behind the hair test

Basically, when any substance is taken into the body, particularly drugs, small elements make their way into the blood stream. This, of course, is what causes the "high" of the drug. Whatever ends up in your blood, from nutritive elements to narcotics, eventually is processed to the parts of your body that grow on a regular basis, namely the hair and the fingernails. The problem with testing for drugs using fingernail clippings is that the elements in the blood are turned into keratin during metabolism and therefore are no longer present in their individual parts. Hair, however, retains the memory and the atomic structure of whatever has been ingested and keeps a record, much as the rings on a tree do.

The length of time for which the test is effective

The effective range for a drug test in an individual’s hair sample will differ according to each individual. In fact, drug usage can be detected as long as that particular hair has been growing, the only time period that may be missed by such a test is a narcotic that has been ingested just prior to the test; usually a period between two to five days. After this time, the drug will start to show up in hair samples.

Standard information on hair drug tests say that they are effective for around ninety days, or three months, and right up to 120 days (four months). This, of course, is based on the average growth rate of a human hair follicle. The idea here is that after that period of time has elapsed, the average person is likely to get a haircut that will result in the loss of the part of the hair follicle that grew during drug usage.

Just as an individual may keep a permanent record of their drug usage by never cutting their hair, so can short hair or a shaved head erase any hair follicle records of drug usage. This need not foil testers, however, as any hair on the body will keep this record.