Usman et al. Egyptian Journal of Forensic Sciences
https://doi.org/10.1186/s41935-019-0119-5
(2019) 9:17
Egyptian Journal of
Forensic Sciences
REVIEW Open Access
Forensic toxicological analysis of hair: a
review
Muhammad Usman1* , Abid Naseer1, Yawar Baig1, Tahir Jamshaid1, Muhammad Shahwar1 and Shazia Khurshuid2
Abstract
Analysis of hair provides useful information regarding drug addiction history or drug toxicity. Keeping in view some
important applications of hair analysis, a lot of work done in the past few decades has been reviewed in this article.
When compared with other biological samples, hair provides a larger window for drug detection. Drugs get
deposited in hair through blood circulation by various mechanisms, after its administration. The deposited drug is
much stable and can be detected after a longer period of time as compared with other biological samples, e.g.,
saliva, blood, and urine. Moreover, segmental analysis can depict multiple or single drug administration by using
sensitive analytical techniques. Complex methods for drug extraction and the high cost of analysis are some
drawbacks of hair analysis. LC-MS and GC-MS are the prominent among other techniques of choice due to high
sensitivity. In this review, detailed knowledge about the drug deposition, extraction, analysis, and application of
results in forensic and clinical cases have been discussed.
Keywords: Forensic science, Toxicology, Hair analysis, Narcotic drugs, Drug of abuse
Background confirmed that they circulate through blood circulation
During the last few decades, tremendous research work and deposit in hair. In 1979, the first research article was
has been done to investigate the different drugs of abuse published regarding the analysis of hair from heroin
and their metabolites in different types of biological users. Morphine, a metabolite of heroine, was found in
samples, e.g. saliva, sweat and hair. In a number of coun- the hair of addicts (Kintz 2017b). It was also found that
tries, biological samples other than urine, are being ex- the concentration of drug varied along the length of the
plored intensively for workplace drug testing, providing hair shaft, which could be correlated with the time
information about chronic intoxication, awarding a driv- period of abuse. Nowadays, GC-MS is commonly used
ing license, clinical toxicology, in criminal justice, in the and reported method for analyzing a drug of abuse from
treatment of addicted patients, postmortem toxicology the hair of addicts.
studies, solving drug-facilitated crimes and in child pro- The major advantage of hair drug testing over blood
tection cases (Allibe et al. 2017; Baumgartner et al. 1979; and urine drug testing is its better inspection window.
Khajuria and Nayak 2017). For analysis of new psycho- Hair drug testing has a better inspection window when
active substances, hair testing is a good complement to compared with blood and urine drug testing, which can
urine testing (Kintz 2017a; Montesano et al. 2017). be characterized as its major advantage (2–4 days for
During the 1960s and 1970s, the hair was analyzed for drug analysis from blood and urine for most of the drugs
the investigation of heavy metals by atomic absorption against weeks to several months, depending upon the
spectroscopy (AAS). Since at that time, analytical tech- length of hair) (Hegstad et al. 2008). Blood analysis and
niques were not sensitive enough to analyze organic urinalysis give short-term information related to drug
compounds particularly the drugs from hair. However, addiction whereas long-term drug history can be traced
by the use of radioactive isotope-labeled drugs, it was by hair analysis (Saitoh 1969).
* Correspondence: ;
1
Narcotic Unit, Punjab Forensic Science Agency, Lahore 53700, Pakistan
Full list of author information is available at the end of the article
© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.
, Usman et al. Egyptian Journal of Forensic Sciences (2019) 9:17 Page 2 of 12
Main text appropriate choice for drug analysis. Beard hair can be
Structure and types of hair collected daily for investigation of the rate of drug de-
Hair is mainly composed of protein, which may range position (Cone et al. 1991).
from 65 to 95% (keratin), lipids 1–9%, 15–35% water,
and less than 1% minerals (Kintz 2017b). Its texture, Growth of hair
color, and composition vary from person to person. Dif- Human hair grows in three developmental stages. The
ferent types of minerals accumulated in the hair may shape and size of the hair root are determined by the
range from 0.25 to 0.95%. About 5 million hair follicles growth phase in which the hair happens to be. The three
are present in an adult. Out of these 5 million hair folli- phases of hair growth are the anagen, catagen, and telo-
cles, approximately 1 million are found in the head. Hair gen phases. The anagen phase may last up to 6years.
follicles are rooted 3–4-mm deep in the skin, in the epi- During this phase, the root remains attached to the fol-
dermis of epithelium (Mangin 1996). The total hair licle for continued growth, giving the root bulb a
length covers its bulb rooted in the follicle through the flame-shaped appearance. The catagen phase may
shaft and ends at its tip. The shaft is comprised of three proceed from 2 to 3 weeks. During this phase, hair con-
layers, i.e., cuticle, cortex, and medulla. Cuticle has some tinues to grow but at a retarded growth rate. In the cata-
ability to maintain its structural features for a longer gen phase, roots acquire an elongated appearance as the
period of time and also have some resistance to chemical root bulb shrinks and are pushed out of the hair follicle.
decomposition. Cortex is the second layer lying under Once the hair growth stops, the telogen phase begins
the protective covering of cuticle. The cortex derives its and the root takes on a club-shaped appearance. By the
major forensic importance from the fact that it is em- next 2 to 6 months, the hair is pushed out of the follicle,
bedded with the pigment granules, which gives hair its causing the hair to shed off naturally (Baumgartner et al.
characteristic color. The color, shape, and distribution of 1989) (Khajuria et al. 2018).
these granules provide important points of comparison The growth of hair does not remain continuous
among the hairs of different individuals. The medulla is throughout the course. It is a cyclic process in which
a collection of cells that looks like a central canal run- hair growth phase alternates with dormant or no growth
ning through the hair. In many animals, this canal is a phase. The actively growing follicles are in the anagen
predominant feature, occupying more than half of the phase. The head hairs grow at a rate of 0.6–1.42 cm/
hair diameter. The presence and appearance of medulla month or 0.22–0.52 mm/day. The rate of growth of hair
vary from individual to individual and even among the depends on location and type of hair. After the growth
hairs of the same individual. Medullae may be classified phase, the hair follicle enters in catagen phase. In this
as continuous, interrupted, fragmented, or absent. Hu- phase, the hair shaft stops growing and shed off (Cart-
man head hairs generally exhibit no medullae or have mell et al. 1991; Kintz 2017b).
fragmented ones and they rarely show continuous
medullation (Kronstrand et al. 1999). Mechanisms of drug incorporation
There are different types of hairs that can be used as a The simple passive transfer is the simplest model that
substitute for drug analysis when there are no scalp hair, explains the deposition of a drug into the hair. Accord-
e.g., axillary (armpit), pubic hair, and arm hair. A num- ing to this model, drugs incorporate in the hair by the
ber of studies have been performed to find out the dif- passive diffusion from the growing cells in hair root, and
ferences in concentrations of drug in various types of when the keratogenesis occur, the drug is transferred to
hairs from the same individual. When the concentration the hair shaft in a tightly bound form. The deposition of
levels of morphine, methadone, phenobarbital, and co- drug in the hair depends on the concentration of drug in
caine were compared in different types of hairs, the blood if the rate of hair growth is constant. This model
highest level of drug quantity was found in axillary hair describes that segmental analysis of hair can predict the
and lowest one was found in the scalp hair. In another presence of the drug in the blood for a specific time
study, the concentration of morphine was determined in interval.
different hair types: 0.4–24.2 ng/mg was found in axillary Complex multi-compartment model is another model
hair, 0.6–27.1 ng/mg in scalp hair, and 0.8–1.34 ng/mg in describing the drug deposition mechanism in hairs. This
pubic hair. The remarkable differences in concentration model is more accepted than the previous one. Accord-
of drug are due to the improved blood supply, ing to it, the drugs incorporate into the hair in three dif-
telogen-anagen ratio, difference in growth rate, and dif- ferent ways.
ferent numbers of apocrine gland. Different types of
hairs grow at different rates, e.g., pubic hair 0.3 mm/day Through blood circulation during hair formation
and axillary hair 0.4 mm/day. The growth rate of beard Through sweat and sebum gland after the formation of
hair is 0.27 mm/day, and it is thought to be the hair
https://doi.org/10.1186/s41935-019-0119-5
(2019) 9:17
Egyptian Journal of
Forensic Sciences
REVIEW Open Access
Forensic toxicological analysis of hair: a
review
Muhammad Usman1* , Abid Naseer1, Yawar Baig1, Tahir Jamshaid1, Muhammad Shahwar1 and Shazia Khurshuid2
Abstract
Analysis of hair provides useful information regarding drug addiction history or drug toxicity. Keeping in view some
important applications of hair analysis, a lot of work done in the past few decades has been reviewed in this article.
When compared with other biological samples, hair provides a larger window for drug detection. Drugs get
deposited in hair through blood circulation by various mechanisms, after its administration. The deposited drug is
much stable and can be detected after a longer period of time as compared with other biological samples, e.g.,
saliva, blood, and urine. Moreover, segmental analysis can depict multiple or single drug administration by using
sensitive analytical techniques. Complex methods for drug extraction and the high cost of analysis are some
drawbacks of hair analysis. LC-MS and GC-MS are the prominent among other techniques of choice due to high
sensitivity. In this review, detailed knowledge about the drug deposition, extraction, analysis, and application of
results in forensic and clinical cases have been discussed.
Keywords: Forensic science, Toxicology, Hair analysis, Narcotic drugs, Drug of abuse
Background confirmed that they circulate through blood circulation
During the last few decades, tremendous research work and deposit in hair. In 1979, the first research article was
has been done to investigate the different drugs of abuse published regarding the analysis of hair from heroin
and their metabolites in different types of biological users. Morphine, a metabolite of heroine, was found in
samples, e.g. saliva, sweat and hair. In a number of coun- the hair of addicts (Kintz 2017b). It was also found that
tries, biological samples other than urine, are being ex- the concentration of drug varied along the length of the
plored intensively for workplace drug testing, providing hair shaft, which could be correlated with the time
information about chronic intoxication, awarding a driv- period of abuse. Nowadays, GC-MS is commonly used
ing license, clinical toxicology, in criminal justice, in the and reported method for analyzing a drug of abuse from
treatment of addicted patients, postmortem toxicology the hair of addicts.
studies, solving drug-facilitated crimes and in child pro- The major advantage of hair drug testing over blood
tection cases (Allibe et al. 2017; Baumgartner et al. 1979; and urine drug testing is its better inspection window.
Khajuria and Nayak 2017). For analysis of new psycho- Hair drug testing has a better inspection window when
active substances, hair testing is a good complement to compared with blood and urine drug testing, which can
urine testing (Kintz 2017a; Montesano et al. 2017). be characterized as its major advantage (2–4 days for
During the 1960s and 1970s, the hair was analyzed for drug analysis from blood and urine for most of the drugs
the investigation of heavy metals by atomic absorption against weeks to several months, depending upon the
spectroscopy (AAS). Since at that time, analytical tech- length of hair) (Hegstad et al. 2008). Blood analysis and
niques were not sensitive enough to analyze organic urinalysis give short-term information related to drug
compounds particularly the drugs from hair. However, addiction whereas long-term drug history can be traced
by the use of radioactive isotope-labeled drugs, it was by hair analysis (Saitoh 1969).
* Correspondence: ;
1
Narcotic Unit, Punjab Forensic Science Agency, Lahore 53700, Pakistan
Full list of author information is available at the end of the article
© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.
, Usman et al. Egyptian Journal of Forensic Sciences (2019) 9:17 Page 2 of 12
Main text appropriate choice for drug analysis. Beard hair can be
Structure and types of hair collected daily for investigation of the rate of drug de-
Hair is mainly composed of protein, which may range position (Cone et al. 1991).
from 65 to 95% (keratin), lipids 1–9%, 15–35% water,
and less than 1% minerals (Kintz 2017b). Its texture, Growth of hair
color, and composition vary from person to person. Dif- Human hair grows in three developmental stages. The
ferent types of minerals accumulated in the hair may shape and size of the hair root are determined by the
range from 0.25 to 0.95%. About 5 million hair follicles growth phase in which the hair happens to be. The three
are present in an adult. Out of these 5 million hair folli- phases of hair growth are the anagen, catagen, and telo-
cles, approximately 1 million are found in the head. Hair gen phases. The anagen phase may last up to 6years.
follicles are rooted 3–4-mm deep in the skin, in the epi- During this phase, the root remains attached to the fol-
dermis of epithelium (Mangin 1996). The total hair licle for continued growth, giving the root bulb a
length covers its bulb rooted in the follicle through the flame-shaped appearance. The catagen phase may
shaft and ends at its tip. The shaft is comprised of three proceed from 2 to 3 weeks. During this phase, hair con-
layers, i.e., cuticle, cortex, and medulla. Cuticle has some tinues to grow but at a retarded growth rate. In the cata-
ability to maintain its structural features for a longer gen phase, roots acquire an elongated appearance as the
period of time and also have some resistance to chemical root bulb shrinks and are pushed out of the hair follicle.
decomposition. Cortex is the second layer lying under Once the hair growth stops, the telogen phase begins
the protective covering of cuticle. The cortex derives its and the root takes on a club-shaped appearance. By the
major forensic importance from the fact that it is em- next 2 to 6 months, the hair is pushed out of the follicle,
bedded with the pigment granules, which gives hair its causing the hair to shed off naturally (Baumgartner et al.
characteristic color. The color, shape, and distribution of 1989) (Khajuria et al. 2018).
these granules provide important points of comparison The growth of hair does not remain continuous
among the hairs of different individuals. The medulla is throughout the course. It is a cyclic process in which
a collection of cells that looks like a central canal run- hair growth phase alternates with dormant or no growth
ning through the hair. In many animals, this canal is a phase. The actively growing follicles are in the anagen
predominant feature, occupying more than half of the phase. The head hairs grow at a rate of 0.6–1.42 cm/
hair diameter. The presence and appearance of medulla month or 0.22–0.52 mm/day. The rate of growth of hair
vary from individual to individual and even among the depends on location and type of hair. After the growth
hairs of the same individual. Medullae may be classified phase, the hair follicle enters in catagen phase. In this
as continuous, interrupted, fragmented, or absent. Hu- phase, the hair shaft stops growing and shed off (Cart-
man head hairs generally exhibit no medullae or have mell et al. 1991; Kintz 2017b).
fragmented ones and they rarely show continuous
medullation (Kronstrand et al. 1999). Mechanisms of drug incorporation
There are different types of hairs that can be used as a The simple passive transfer is the simplest model that
substitute for drug analysis when there are no scalp hair, explains the deposition of a drug into the hair. Accord-
e.g., axillary (armpit), pubic hair, and arm hair. A num- ing to this model, drugs incorporate in the hair by the
ber of studies have been performed to find out the dif- passive diffusion from the growing cells in hair root, and
ferences in concentrations of drug in various types of when the keratogenesis occur, the drug is transferred to
hairs from the same individual. When the concentration the hair shaft in a tightly bound form. The deposition of
levels of morphine, methadone, phenobarbital, and co- drug in the hair depends on the concentration of drug in
caine were compared in different types of hairs, the blood if the rate of hair growth is constant. This model
highest level of drug quantity was found in axillary hair describes that segmental analysis of hair can predict the
and lowest one was found in the scalp hair. In another presence of the drug in the blood for a specific time
study, the concentration of morphine was determined in interval.
different hair types: 0.4–24.2 ng/mg was found in axillary Complex multi-compartment model is another model
hair, 0.6–27.1 ng/mg in scalp hair, and 0.8–1.34 ng/mg in describing the drug deposition mechanism in hairs. This
pubic hair. The remarkable differences in concentration model is more accepted than the previous one. Accord-
of drug are due to the improved blood supply, ing to it, the drugs incorporate into the hair in three dif-
telogen-anagen ratio, difference in growth rate, and dif- ferent ways.
ferent numbers of apocrine gland. Different types of
hairs grow at different rates, e.g., pubic hair 0.3 mm/day Through blood circulation during hair formation
and axillary hair 0.4 mm/day. The growth rate of beard Through sweat and sebum gland after the formation of
hair is 0.27 mm/day, and it is thought to be the hair
