What Is Normal Hair? Advancements in Hair Imaging Techniques

The document discusses advancements in hair imaging techniques, particularly trichoscopy, and their impact on understanding normal hair characteristics and diagnosing hair diseases. Trichoscopy, which uses dermoscopy or videodermoscopy, allows for the visualization and measurement of hair without plucking, and has revealed that hair thickness varies across different scalp areas in healthy individuals. For example, the mean hair thickness was found to be 0.061 mm in the frontal area and 0.058 mm in the occipital area, with the temporal area having intermediate values. The proportion of thin, medium-sized, and thick hairs in healthy Caucasian females was approximately 6%, 21%, and 73%, respectively, indicating that a limited hair-shaft diameter heterogeneity is normal and not necessarily indicative of hair miniaturization seen in androgenic alopecia. Trichoscopy has also enabled the identification of new hair diseases, such as alopecia areata incognita, and has improved the diagnosis of hair shaft abnormalities like monilethrix, woolly hair syndrome, and others. The authors suggest that trichoscopy will likely expand the spectrum of defined hair and scalp diseases and improve diagnostic clarity, but it is uncertain how quickly this will translate into new treatment options.