Hair drug tests are can be administered to detect the presence of several types of drugs including cannabis.

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Unlike urine tests, which can detect the presence of cannabis up to a month after cannabis use depending on the user’s frequency of use, hair follicle drug tests can detect cannabis up to 90 days post-cannabis use, even if cannabis consumption is infrequent.

You may be required to take one of these tests if you are applying for a new job. Your current employer may also conduct routine or random drug screening. If you are in a drug rehab program, a hair follicle drug test can be used to track any patterns of drug use.

If you are on parole, a hair follicle drug test may be used at random or for a routine drug screen. Although your consent is typically required before you take a drug test, failing to give it can lead to penalties such as lost employment opportunities, mandatory rehab, or imprisonment. 

Here is everything you need to know about how these drug tests work and how to beat them. 

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Detoxing for a Hair Drug Test 

Hair follicle drug tests are extremely difficult to pass if you have used cannabis in the last 90 days. This is because the cannabinoid metabolites become a permanent part of the hair cells.

As long as you grow hair, evidence of cannabis use will be present. Unlike with a urine test, you cannot use a synthetic replacement. It will be obvious to the lab technician if the hair is real or synthetic. 

However, there are some detox products designed specifically to cleanse the hair and scalp of toxins that would point to drug use.

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Test Clear provides extremely sensitive hair follicle drug tests that you can administer to yourself at home to determine whether your hair will screen positive or negative for cannabis. 

Test Clear also provides two detox products: Zydot Ultra Clean Shampoo and Old Style Aloe Toxin Rid Shampoo. Customer reviews are overwhelmingly positive. 

Unfortunately, no test is foolproof. If you know that you will be required to take a drug test, the safest way to guarantee a negative test result is to abstain from drug use as soon as possible.

You can help the body expedite its natural system of detoxification by eating a low fat, sodium, and sugar diet, exercising, and drinking lots of water.

These methods work best for urine tests. Abstaining from cannabis consumption for at least 90 days is the best way to beat a hair follicle drug test. 

How a Hair Follicle Drug Test Works

Hair follicle drug tests are able to detect the use of the following drugs within a 3-month period:

  • Cannabis 
  • Amphetamines 
  • Cocaine
  • Opiates
  • Phencyclidine 

These tests can be administered at home or work or in a more clinical setting such as a hospital or lab. The accuracy of the test is not affected by washing or treating your hair with styling products. It is also likely that the test will be supervised.

Depending on the test kit requirements, 70 to 120 hairs will be collected from as close to the scalp as possible. To avoid creating a bald spot, the hair collector can choose samples from different places on the head.

Body hair can be used as an alternative for those who do not have a lot of head hair.

A Child and Adolescent Psychiatric Clinics of North America study determined that each strand of hair must be between 0.5 and 1.5 inches in length for accurate results.  Lab technicians can determine a negative test within 24 hours. A screening test called ELISA is used to identify the presence of any illicit drugs. If the ELISA test comes back positive, another test is administered to confirm those results.

72 hours after the positive ELISA test, a gas chromatography/mass spectrometry test is used to confirm the positive test and to identify which drugs have been detected in the hair. 

A positive hair follicle drug test indicates that drugs have been used in the past 90 days. It can also identify the specific drugs used. However, it cannot identify the date within the 90-day period that the drugs were used. This is because the rate of hair growth varies greatly between individuals.

The 2-step testing process is designed to avoid inaccurate results. However, a 2017 Addiction study suggests that false positives, as well as false negatives, are possible.

The study compared testing results with self-reported cannabis use. The results led the researchers to conclude that hair testing is “an unreliable marker of substance abuse.”

It is also possible for a hair drug test to screen positive if you have used a prescribed opioid painkiller. You may be required to demonstrate evidence of your prescription if this occurs. 

How Do Drugs Get in the Hair?

When cannabis is consumed—be it through inhalation, ingestion, or dermal application—the cannabinoids eventually enter the bloodstream. From there, cannabinoids are metabolized until they are eliminated by the digestive and excretory systems.

However, the lipophilic cannabinoids will also disperse to adipose (fatty) tissue, where they can remain for many weeks and even months.  Hair follicles are regulated by adipose tissue, and this may explain how cannabinoids and their metabolites are detected in hair.

Hair can be taken from any part of the body to screen for drugs since all hair grows from hair follicles. However, hair takes time to grow.

This means that hair follicle drug tests are not ideal for detecting immediate drug use. It takes about a week for hair to grow enough for drugs to be detected in the hair strand.