A 5-panel hair follicle drug test determines patterns of substance use over an extended period. This form of screening analyzes a small hair sample to detect specific drugs and their breakdown products, known as metabolites. The test provides a comprehensive look at an individual’s drug history, distinguishing it from tests that only look for recent use. It is often employed in employment settings, legal proceedings, and for monitoring long-term substance use.
The Five Drug Classes Screened
The “5-panel” designation refers to the five major categories of drugs screened, which align with common federal guidelines. The test looks for metabolites of cocaine, a powerful stimulant, and amphetamines, a class that includes methamphetamine and ecstasy (MDMA).
The panel also includes opioids, covering natural and semi-synthetic narcotics like codeine, morphine, hydrocodone, and heroin metabolites. The fourth class is Phencyclidine, commonly known as PCP. Finally, the test screens for marijuana metabolites, specifically the primary compound related to cannabis use (THC-COOH).
How Drugs Enter the Hair Follicle
The mechanism by which drugs are recorded in hair is a physiological process linked to hair growth. Once consumed, the substance is metabolized, and both the parent drug and its metabolites enter the bloodstream. The blood circulates these compounds to the hair papilla, which is the base of the hair follicle.
The hair follicle is essentially a miniature organ where hair cells are produced. As the hair shaft is formed, drug compounds and their metabolites are incorporated into the hair’s structure, primarily within the core layers of the growing hair. This incorporation happens as the hair is being synthesized, effectively creating a permanent record of substance use. The hair then grows out from the scalp, allowing the test to look back in time.
Incorporation occurs through passive diffusion from blood capillaries surrounding the follicle and from the sebaceous and sweat glands. Once embedded in the keratinized hair shaft, the drug metabolites are stable and cannot be easily washed out by normal hygiene. This process gives the hair test a significantly longer detection window compared to urine or saliva tests.
Sample Collection and Detection Window
The standard procedure involves collecting a small lock of hair cut close to the scalp. The collector typically gathers about 90 to 120 strands (approximately 100 milligrams). This sample is usually taken from the back of the head, known as the vertex, to ensure accurate growth representation.
The length of the hair sample determines the period of drug history examined. Scalp hair grows about one-half inch per month. Therefore, a standard 1.5-inch sample, measured from the scalp, provides a detection window of approximately 90 days. If head hair is unavailable, body hair may be collected, but its slower, less predictable growth rate provides only a general overview of use, sometimes up to a year.
A drug can be detected earliest about 7 to 10 days after use, accounting for the time it takes for the hair containing metabolites to grow out from the scalp. This means the test is not suitable for detecting very recent use. The consistent growth rate of head hair allows the laboratory to provide a rough timeline of use over the 90-day period.
Reliability and Limitations of the Test
The hair follicle test is considered highly reliable for detecting patterns of repeated or chronic substance use over its 90-day window. Laboratories employ a two-step process, beginning with an initial immunoassay screen, followed by a more precise confirmation test using methods like Gas Chromatography-Mass Spectrometry (GC-MS) for any presumptive positive results. This confirmatory testing provides a numerical result and helps rule out false positives.
Labs mitigate the issue of external contamination, such as exposure to secondhand smoke containing drug residues. Reputable facilities wash the hair sample extensively before testing and analyze for both the parent drug and its metabolite. The presence of the metabolite deep within the hair shaft strongly indicates ingestion rather than external contact. Hair color can also influence results, as some drug compounds bind more readily to melanin, the pigment found in darker hair.
The test focuses on detecting repeated use; a single, isolated instance may not result in a positive test because the concentration may not exceed the established cut-off levels. Furthermore, harsh cosmetic treatments like bleaching and dyeing can alter the hair’s chemical structure and reduce metabolite concentration, though this does not reliably mask chronic drug use.