Current status of keratinized matrices in Toxicology: Comparison of hair and nails

Abstract Nails are a keratinized matrix that has been proposed as an alternative to hair to evaluate long‐term and retrospective consumption of drugs of abuse and pharmaceuticals. This matrix has been gaining interest in recent years, with new studies focusing on the analysis of fingernails and/or toenails for different substances. However, nails and hair present differences in structure, growth, and incorporation pathways that may affect drug incorporation and analysis and complicate the interpretation of the results. To better understand the