Hair Publisher



Nikfar S¹ ; Mozaffari S^{1, 2} Show Affiliations
Source: Encyclopedia of Toxicology# Fourth Edition: Volume 1-9 Published:2023

Abstract

Hair grows on the external body skin of mammals and is composed of a protein called keratin. Each strand of hair is made up of three layers named medulla, cortex, and cuticle. Hair growth cycle begins in the hair follicle, the part of hair that is beneath the skin. Cortex contains melanin granules which are responsible for hair color. Melanin is divided into eumelanin, the dominant pigment in brown and black hair, and pheomelanin, the dominant pigment in red hair. Some toxic substances can inactivate the production of melanin and result in hair color change. Due to reflecting composition of elements in body tissues, hair is used as an excretory tissue for testing toxicants. Hair can yield an informative retrospective documents on both acute and chronic exposure to chemical substances. Hair analyses gain a remarkable notice in forensic toxicology in terms of drug abuse, doping, and poisoning. Opioids, antidepressants, antipsychotics, and amphetamines can be detected in hair analysis. Currently, reliable different methods do exist to detect and measure various chemicals in hair. However, the strengths and weaknesses for each method should be kept in view. The specific growth cycles of each strand of hair, and challenging interpretations of results, in addition to expensive techniques, are some notable limitations for hair analysis. © 2024 Elsevier Inc. All rights reserved.