Review on Toxicology Testing in Hair.

Background: Hair toxicology is a useful tool for detecting long-term drug use. This method offers several advantages, including the ability to trace historical patterns of drug intake. However, drug incorporation into hair is complex, influenced by numerous factors such as hair structure, physiological differences, external contamination, and the chemical properties of drugs. A comprehensive understanding of these factors is critical to accurately interpret hair toxicology results in both clinical and forensic settings.

Content: The anatomy of hair plays a vital role in drug incorporation. Drugs can enter the hair via diffusion from the bloodstream, by passive deposition through sweat or sebum bathing the hair, or through external contamination. The analysis of drug incorporation has evolved significantly over time, and it is now possible to detect drug exposure even after a single ingestion. However, several factors such as decontamination protocols, extraction methods, melanin content (hair color), growth rates, contamination from drug particulates, and cosmetic hair treatments may affect the accuracy of hair toxicology results. Guidelines by expert societies have been published, but variations in sample preparation and analysis techniques remain.

Summary: While hair toxicology holds promise for detecting long-term drug exposure, many variables must be considered to ensure accurate interpretation. Differences in physiological properties and external factors can complicate the results. Harmonized protocols and advanced techniques are necessary to minimize biases, particularly regarding racial differences in drug incorporation. Future research should aim to further harmonize methodologies and address these challenges to enhance the reliability of hair toxicology testing.