Testing for drugs and in particular testing hair for drugs is becoming far more commonplace, especially in the US, UK and the EU. This approach to drug testing has a significant advantage over other detection methods such as urine, blood and saliva, in that it provides a far greater period of time for which drugs can be detected. (This is commonly known as the detection window). It is possible to detect drugs for several months - even years if the hair has been allowed to grow for that amount of time. In most cases however, tests usually involve 90 day detection: This compares to just 4-5 days for fluid based testing (or in chronic cases of marijuana misuse, 28 days)
Approximately 50 hair follicles are needed for successful hair test results. This is about the thickness of the end of a shoelace, meaning that most people would show no obvious signs that any hair had been taken unless their hair is particularly short.
The cost of hair testing is higher than urine based tests - which are the only other viable method of achieving top-quality test results. Testing using blood is not commercially available partly due to the challenges in taking a sample in the first instance.
A typical hair folical test costs in the region of £60-£70 for preparation of the sample (which involves turning the hair from a solid to a liquid) and then a further £40-50 per drug type required for detection. This compares to an approximate charge of £60-75 for laboratory testing of urine which will pick up illegal substances across all drug classes.
The biggest question asked of course is how to pass hair tests. Very simply, there is only one definite way in which to guarantee this - Don’t take drugs!