Hair Drug Testing


Hair testing analyses the hair shaft for the presence of embedded drug molecules. Hair testing eliminates false negatives that can be the result of external contamination. Hair is nourished by the blood and when drugs enter the bloodstream, they are carried to and deposited in the hair. Hair drug tests cannot be faked or beaten by the use of shampoos, hair dye, or any other types of chemicals or adulterants..

Currently, most drug testing is performed on urine samples, but most drugs are undetectable in the urine after after a few days. This is where hair drug testing comes in useful, as the time frame that can be analysed is much longer than for urine or saliva drug testing.

Hair testing provides a reliable window of detection of past use. Hair shows patterns of drug use, accurately determining specific drugs used and the time frame in which they were used. Equally important, hair testing can also be used to definitively prove that the subject has not used any controlled substance.

Facts about hair testing

Hair analysis is the most reliable and accurate way to identify drug use. Testing only requires a small hair sample cut near the scalp and identifies the extent of drug metabolites located inside the shaft.

Theoretical Basis of Detection

Most drug tests are carried out on urine samples, but many drugs are undetectable using this method after a few days.  Some drugs do have a long time frame of detection using urine drug tests. Cannabis, for example, can be detected for a few weeks in habitual users, However occasional use would be undetectable after this time.

Most drugs leave permanent markers in the hair shaft, allowing for accurate screening to detect use of drugs months, even years with long hair, in the past.

Detecting drugs in hair

Unless urine collection is observed directly it is possible for a drug user to provide a fake specimen and beat a urine drug test. A hair drug test cannot be beaten. (We do not know of any commercial adulterants or tricks that will successfully ‘trick’ a hair drug test.)

Hair drug testing offers a picture of drug use or abstention measured in months instead of days. Hair testing offers a number of benefits over urine testing, including:

  • Can detect drug use over months, as opposed to a couple of days.
  • Inexpensive and saves time, it would take 18 urine samples over three months to give as much information as one hair test.
  • No need for random testing
  • Collection, transportation, and storage are easier.
  • Hair analysis is more reliable and dignified than urine.
  • Identifies frequency of use, differentiating between frequent use, occasional use, or a one time incident.

Incorporation of Drugs into Hair

On average, hair grows about 13mm per month. Each individual follicle is nourished by its own supply of blood, which provides the nutrients that hair needs to grow. Drugs are absorbed into the bloodstream and circulated to the entire body, including the hair. As hair grows, it takes whatever is in the blood, both nutrients and drugs, and incorporates them into the hair, where they remain indefinitely. Hair needs only be 40mm ong to provide a 3 month snapshot of whether an individual has used drugs.

Compared with other types of drug testing, such as urine tests, hair analysis detects drugs use over a longer period. Urine tests cannot detect most drugs unless used within the previous few days. The one notable exception is cannabis, which can be detected for a period of a few weeks, depending on how much and how frequently it is used.

One problem with urine drug tests is that  savvy drug users can fairly easily substitute fake samples to beat the drug test. With hair testing, the only limit is the length of the subject’s hair, and samples cannot be substituted. 13mm of hair from the head gives information on the past thirty days, while the industry standard is to test 40mm, yielding a ninety day profile of use.

In the event head hair is unavailable, body hair can also be tested. External chemicals such as shampoo, bleach, and even cannabis smoke, has not been shown to impact results.

NOTE: In certain cases, cannabis use may not be detectable in a hair sample because the THC metabolites are not always able to bind to the hair shaft. This can be attributed to the type and quality of cannabis used, or if it is mixed with tobacco. These situations may lead to a false negative.

Studies show that teenagers who use cannabis are more likely than to use other, more dangerous drugs than those who have never used cannabis. If you suspect that your child is using cannabis, remember that a hair test will also detect any other drugs they may have used.

For more information about Hair Drug Testing from Zoom Testing, contact us.

Photo Credit: “Flame Hair” (CC BY 2.0) by calxfornia