Brief descriptions of the principles of prominent methods used to study the penetration of materials into human hair and a review of examples of their use

Abstract

Consumers are attracted to the latest fashion trends and different looks. This drives the search for novel hair treatments. Some chemicals present in hair treatment products can penetrate the hair shaft. These materials can either nourish or injure the hair cortex. Different techniques have been used to investigate the mechanism of molecule penetration and the conditions under which penetration occurs. This article reviews the techniques applied for this purpose. Various microscopy techniques are used to capture clear and colourful images to determine the diffusion pathways and the exact location of the molecules under study. However, the laborious sample preparation often leads to sample destruction since cross‐sectioning is often required. While various other techniques have been successfully used for investigating the penetration methods, most of these require different amounts of work to be put in for sample preparation and instrumentation. Several spectroscopic techniques have been used to study the penetration of the molecules because of the high levels of accuracy and the quick response time of these techniques. Moreover, the samples are not damaged during the investigation.

Impact of Hair Damage on the Penetration Profile of Coconut, Avocado, and Argan Oils into Caucasian Hair Fibers

“…Several techniques have been adopted to assess the penetration properties of molecules in hair [18]. More sophisticated methods of analysis are often required to investigate the molecular interactions that drive the diffusion of materials into the hair structures, such as spectroscopy, spectrometry, and tomography, among others [18][19][20][21][22][23][24][25][26]. However, these techniques frequently involve laborious sample manipulation and/or high operational costs, limiting their widespread application in an industrial context.…”

Rice Derivatives in Hair Protecting

“…Hair structure characterization and the evaluation of its physical and mechanical properties are essential for the development of hair care products. The evaluation of the effectiveness of hair care products can be carried out in vitro with instrumental techniques generally endowed with a high sensitivity [5][6][7]. The advantages of these techniques, compared with subjective evaluation (test in use, salon test), are (i) no need for a panel of volunteers, (ii) the use of standardized hair strands, (iii) quick evaluation, and (iv) the use of standardized test conditions.…”

“…The advantages of these techniques, compared with subjective evaluation (test in use, salon test), are (i) no need for a panel of volunteers, (ii) the use of standardized hair strands, (iii) quick evaluation, and (iv) the use of standardized test conditions. Various techniques are used [5][6][7].…”

“…Microscopy and image analyses are used to study the structure of the hair, the penetration of materials, and the presence of substances deposited on the hair and to evaluate its damage [6]. Various studies have been performed by fluorescence microscopy (conventional and confocal) [6,8], by scanning electron microscopy (SEM) [7,9,10], by transmission electron microscopy (TEM) [7,11,12], and by atomic force microscopy (AFM) [13,14].…”