How Hair Drug Testing Works

Hair drug testing is often considered to be one of the more thorough forms of drug testing. An inch and a half of hair, for example, can yield results of which and how many drugs were taken over a ninety-day period. Hair testing can find the five basic illegal substances, including cocaine, marijuana, opiates (codeine and morphine), amphetamines (meth and ecstasy), and phencyclidine (PCP). For a standard hair test, a sample of 40 to 50 strands, or the size of a shoelace, should be taken from near the scalp line.

With a inch and a half strand, each half an inch represents a month and can indicate which substances and how much of (or how regularly) the substance was used. A longer strand of hair, however, won’t show hair from a longer time period, although three inches in length from the root can give a representation of which substances were used over six months. In addition, a substance will show up in the hair near the scalp four to five days after taking it. If you don’t have hair near the scalp, body hair can be taken but, as body hair grows slower, tests may bring up any substances that were taken during the course of a year and won’t be placed at an exact time.

Is it possible for a hair drug test to be altered in any way? If you’re around external substances, such as being around those smoking pot, for example, the substance won’t affect a drug test, as the proteins in the hair are being tested. But over-the-counter medications can sometimes make a stand of hair test positive for substances by enzyme-immunoassay antibodies. In this case, the hair goes through a gas chromatography mass spectrometry test to clarify results. Hair products, in addition, don’t affect a drug test, although hair that is severely damaged to the point of breaking, or cortex damage, may give different results. Detox shampoos, similarly, won’t rinse the substance from the hair but, in many cases, the molecules from the detox shampoo will be embedded in the hair shaft.