Hair Follicle Drug Testing Facts
A strand of hair is as unique as a fingerprint. Due the process that goes into growing hair, many substances that are present in your body will show up in trace elements in your hair. This is why many pre-employment screening processes include drug screening with a hair follicle drug test.
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Parameters
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A hair screening for drugs can determine a history of drug use as far back as 90 days into your past out of a strand of hair as short as 1/2 inch. The longer the hair shaft is, the further back the screening can go. A longer hair will be able to detect drug use for a longer period of time than a shorter hair.
Face vs Body
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Certain hairstyles, such as a shaved head or a short, military-style haircut, may prevent the collection of hair from on top the head. In this case, hair collected from the body is usually taken. Body hair is an excellent substitute for hair from the head, and can give as accurate a picture of past drug use as hair from the head. Places that hair can be collected from include eyebrows, eyelashes, underarm, chest or leg hairs.
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Accuracy
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Currently, a drug screening test using hair is considered to be more accurate than urine or blood screenings for pinpointing long-term and low-level drug use. Forensic tests on hair are admissible in court as evidence in murder cases. However, because all hair structures are different, this evidence must usually be corroborated by other sources.
Testing
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Hair is typically tested through a process called radioimmunoassay, or RIA. RIA uses radioactive substances to determine the presence of specific antigens. Findings from the RIA are typically confirmed in a separate test using mass spectrometry,
Other Information
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The trace elements that may be present in the hair are inside the structure of the hair. It is therefore impossible to 'detox' the hair. A number of companies offer shampoos that they claim will cover the presence of any drug, but most hair testing facilities thoroughly clean hair samples before testing them to remove any traces of surface contaminants, including dirt, oils, drug residue or shampoo and detergents.
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References
Resources
- Photo Credit Photo by J. Durham
