Hair analysis

Hair analysis
Medical diagnostics
Schema depicting how human hair appears in a scanning electron microscope
HCPCS-L2	P2031
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Hair analysis may refer to the chemical analysis of a hair sample, but can also refer to microscopic analysis or comparison. Chemical hair analysis may be considered for retrospective purposes when blood and urine are no longer expected to contain a particular contaminant, typically three months or less. Its most widely accepted use is in the fields of forensic toxicology and, increasingly, environmental toxicology. Several alternative medicine fields also use various hair analyses for environmental toxicology but these uses are controversial, evolving and not standardized.

Microscopic hair analysis has traditionally been used in forensics as well. Analysts examine a number of different characteristics of hairs under a microscope, usually comparing hair taken from a crime scene and hair taken from a suspect. It is still acknowledged as a useful technique for confirming hairs do not match, but the ability of the field to identify a specific person has fallen into disrepute after DNA analysis showed that many claimed matches from this technique were false.

Hair analysis is used for the detection of many therapeutic drugs and recreational drugs, including cocaine, heroin, benzodiazepines and amphetamines. Hair analysis is less invasive than a blood test, if not quite as universally applicable. In this context, it has been reliably used to determine compliance with therapeutic drug regimes or to check the accuracy of a witness statement that an illicit drug has not been taken. Hair testing is an increasingly common method of assessment in substance misuse, particularly in legal proceedings, or in any situation where a subject may have decided not to tell the entire truth about his or her substance-using history. It is also used by private employers who test their employees. Hair analysis has the virtue of showing a 'history' of drug use due to hair's slow growth. Urine analysis might detect drugs taken in the past three days; hair analysis can sometimes stretch back as far as a month, although certain cosmetic treatments (e.g. dyeing hair) can interfere with this. Hair analysis has the ability to measure a large number of potentially interacting elements, although that trait is shared with many other drug tests.