Hair Research Articles

Force-triggered density gradient sedimentation and cocktail enzyme digestion treatment for isolation of single dermal papilla cells from follicular unit extraction harvesting human hair follicles.

Hair follicles (HFs) are dynamic structures which are readily accessible within the skin that contain various pools of stem cells with broad regenerative potential, such as dermal papilla cells (DPCs), dermal sheath cells, and epithelial HF stem cells. DPCs act as signalling centres for HF regeneration. The current method for isolating human DPCs are inefficient. These methods struggle to obtain freshly isolated original DPCs and do not maintain the characteristics of DPCs effectively. In this study, two simple but more efficient methods were explored. Force-triggered density gradient sedimentation (FDGS) and cocktail enzyme digestion treatment (CEDT) were used to isolate purified DP spheres from human HFs, obtaining purified freshly isolated original DPCs from DP spheres. The expression profiles of isolated DPCs were tested, and gene expression of DPC-specific markers were analyzed using immunofluorescence staining, RT-qPCR and western blot. The 10% Ficoll PM400 was determined as the optimal concentration for FDGS method. Primary DPCs, DSCs and HFSCs were isolated simultaneously using the FDGS and CEDT method. The expression profiles of fresh DPCs isolated using the FDGS and CEDT methods were similar to those of traditionally isolated DPCs. DP-specific markers were expressed at significantly higher levels in freshly isolated DPCs than in traditionally isolated DPCs. Compared to traditional methods, the presented laboratory protocols were able to isolate fresh DPCs with high efficiency, thereby improving their research potential.

Insights into structural and proteomic alterations related to pH-induced changes and protein deamidation in hair.

The hair shaft is often exposed to shampoo and haircare products that have unknown or varying pH levels. These products contain a combination of surfactants and other active ingredients to treat the hair or the scalp. As amphoteric proteins, hair keratins have limited buffering capacity, so variations in pH can have multifaceted impacts on them. However, there is limited knowledge about how pH affects keratins and keratin-associated proteins (KAPs). Therefore, this study aims to examine the effects of varying pH levels (pH 3-pH 12) on hair structure and analyse consequent alterations in the hair proteome using mass spectrometry-based proteomics. A scanning electron microscope was used to examine changes in hair-shaft morphology due to exposure to various pH levels, while mass spectrometry was employed to analyse protein alterations. We found that exposing the hair shaft to varying pH levels led to specific effects on the cuticle, including cuticle lifting at certain pH levels, while proteomics analysis identified alterations in the hair proteome along with significant deamidation of keratins types I and II and KAPs. More pronounced effects were observed at extreme acidic conditions (pH 3) and alkaline conditions (above pH 8) on both hair morphology and hair proteins. pH levels between pH 5 and pH 7 had minimal impact on hair structure and proteins, suggesting that haircare products with pH in this range are ideal for hair-shaft health. In contrast, alkaline pH levels were found to negatively affect hair. The structure evaluation and proteomics data emphasize the critical role of pH in hair health. The extreme acidic or alkaline pH impacts the hair structure and hair proteins. The study highlights the optimal pH range for maintaining healthy hair.

The kinetics of moisture sorption by hair.

The rate process of moisture sorption by human hair has been analysed in order to hints for helping deepen knowledge on the hair structure and to explain the behaviour of hair in response to moisture. The isotherms of moisture sorption by hair were recorded, via dynamic vapour sorption (DVS), for untreated (virgin) and treated (heat-shaped and bleached) hair, as well as for separated cuticle and cortex. By considering that, during moisture uptake, the hair fibres also swell, it is possible to introduce a time-dependent rate constant for describing the kinetics of the moisture sorption. This model allows for clearly separating the moisture sorption processes occurring in Cuticle and in Cortex and for proposing a role of chain entanglement in the two main compartments of the fibre. It may also provide some hints on the structural changes occurring in the fibre after different cosmetic treatments. The influence of the weight of the sample on the kinetics of the sorption process has also been noted and quantified. The analysis pointed to a transition occurring at around 30% relative humidity, assigned to the opening of the hair inner structure, and accommodation of more water molecules. This allowed for an estimate of the value of the activation energy of the water molecules reacting with the active sites, which was found to be in good agreement with results published in the literature. The analysis of the kinetics of moisture sorption by hair was shown not only to provide information on the chain entanglement inside the fibre and the effect of cosmetic treatments but also to demonstrate and quantify the influence of fibre density on the sorption process. It is thus suggested that, along with examination of the hysteresis, the analysis of sorption kinetics helps reveal a more complete picture of hair moisture management.

Determining effective waste human hair hydrolyzing parameters combination and its typical physicochemical characteristics in synthesizing liquid nitrogenous organic fertilizer

Discarded Human hairs are considered as waste material in most parts of the world and its accumulation causing several environmental problems. However as a potential material resource, human hair has the advantage that it is completely biodegradable, renewable and available in every locality. Thus reutilizing human hair cut discards with a target of extracting a particular major nutrient supply, namely nitrogen, carbon, sulfur and so forth, can create a positive impact on solving soil’s infertility problems and less productivity issues of concerned agrarian communities. This study has tried to develop waste human hair based bio-fertilizer by primarily identify the better performing hydrolyzing mixture rang of formulation (H5), ratio of human hair waste mass to aqueous hydrolyzer mixture usages (1:5), favorable reacting time ( 90 min) and temperature ( 70 oC) values progressively. Then the physicochemical characteristics were analyzed to reveal the resulted final product’s viscosity (~ 76.0 cp.), density (~ 1.17 gm/l), pH (~ pH 9), organic nutrients availability concerning primary Macronutrients (~ 18:0.03:1 N-P-K ratio ), Secondary Macronutrients (~ 0.13:0:7 Ca-Mg-S ratio) and other trace micronutrient constituents; which are considered as requirements for the soil nutrient enrichments and plant growths.

Biomimetics through bioconjugation of 16-methylheptadecanoic acid to damaged hair for hair barrier recovery

The primary component of the lipid barrier on human hair, which is essential for defense against aging and environmental stresses, is 18-methyleicosanoic acid (18-MEA), which provides hydrophobic properties and protective benefits. Since 18-MEA cannot be regenerated once damaged, developing technology that can permanently bind alternative materials to hair is critical. Once 18-MEA was removed from hair via X-ray photoelectron spectroscopy (XPS), pentaerythritol tetraisoosterate (PTIS) was hydrolyzed and observed via gas chromatography/mass spectrometry (GC/MS) to confirm that it mimicked 18-MEA, and 16-methylheptadecanoic acid (16-MHA) was obtained at pH 4 or lower. 16-MHA was bioconjugated to damaged hair from which 18-MEA was removed via a carbodiimide reaction using polycarbodiimide. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) confirmed that 16-MHA remained on the surface of the bioconjugated hair even after washing. Observation of the endothermic reaction of moisture in hair via a differential scanning calorimetry (DSC) and evaluation of the moisture content confirmed that the physical properties of hair enriched with 16-MHA were similar to those of virgin hair. This biomimetic approach has been shown to restore both external structural integrity and internal moisture homeostasis.

Stimulation of Hair Growth Effect by Fermented Ginsenosides Using Levilactobacillus brevis THK-D437

Hair growth is crucial for physiological functions and psychological well-being, leading to an increasing demand for research in this area. While low-molecular ginsenosides have been shown to promote hair growth in mice, studies on their effects are limited, and there is a lack of research examining the impact of ginsenoside fermentation products derived from lactic acid bacteria. This study investigated the hair-growth-promoting effect of fermented ginsenoside by fermentation of Levilactobacillus brevis THK-D437, which was isolated from the traditional Korean fermented food kimchi and features high β-glucosidase activity. In the cell-based MTT assay, the proliferation rate was increased by 25% in the fermented ginsenoside-treated group on human hair dermal papilla cells (HHDPCs). In the alopecia mouse model study (C57BL/6 mouse model), enhanced hair growth was observed in the fermented ginsenoside-treated mouse groups. Tissue histological analyses showed that the number of hair follicles and the thickness of the epidermis, respectively, were increased in the fermented ginsenoside-treated mouse groups. These results suggested that fermented ginsenoside has a promoting effect on hair growth and a retarding effect on the catagen stage. Therefore, fermented ginseng products might be a new potential therapeutic candidate for promoting hair growth.

Trichosonography: ultrasound of alopecias and hair disorders.

Trichology is the area of dermatology that focuses on the study, diagnosis and management of the different types of alopecia and hair and scalp disorders. In recent years, there have been great advances in the non-invasive diagnosis of these conditions, especially with trichoscopy and more recently with sonography. High frequency ultrasound study of the scalp, for which we propose the name of "trichosonography", may represent a valuable technique in the evaluation of both clinical and subclinical abnormalities of the hair follicle and the innermost layers of the skin, which are otherwise inaccessible to trichoscopy. The purpose of this pictorial essay is to offer a descriptive approach to the clinical and ultrasound findings of the main hair and scalp disorders.

Early diagnosis of immunodeficient patients with partial albinism: The role of hair study and peripheral blood smear.

Primary immunodeficiency diseases (inborn errors of immunity) with partial albinism are a group of autosomal recessive syndromes including Chediak Higashi Syndrome (CHS), Griscelli Syndrome type 2 (GS2), Hermansky-Pudlak Syndromes type 2 and 10 (HPS2, HPS10), Vici syndrome and P14/LAMTOR2 deficiency. Twenty-five patients including 10 CHS, 10 GS2, and 5 HPS2 were evaluated in this study within the last 10 years. Five cases with oculocutaneous albinism (OCA) and 5 healthy subjects without albinism were used as two control groups. Genetic analyses were performed by whole exome or panel sequencing or targeted Sanger sequencing. Subsequently, leukocyte granules in peripheral blood smear and hair shaft were examined as screening tests. Giant granules were only presented in the leukocytes cytoplasm of 10/10 CHS patients. The uneven cluster of pigments and giant melanin granules in hair samples were observed in 10/10 GS2 and 10/10 CHS patients, respectively. In both 5/5 OCA and 5/5 HPS2 patients, there were regular pigments in the middle of hair shafts. Genetic analyses were performed for all patients, revealing 7 novel variants in LYST gene for CHS patients and 4 novel variants in AP3B1 for HPS2 patients. Receiving hematopoietic stem cell transplantation (HSCT) in a timely manner is crucial in CHS and GS2 patients; therefore, screening tests may provide a vital clue for early diagnosis in these patients. However, the final confirmation of CHS, GS2, and HPS2 disorders is done by genetic assay.

Constructing HairDB to facilitate exposome research using human hair

This study introduces HairDB, an online database serving as a comprehensive repository of hair-related chemicals for exposome research. HairDB was created via an integrative approach. It first extracted 4,184 unique hair-related chemicals through text mining of over 34 million PubMed abstracts and 5.2 million PubMed Central articles, followed by manual data checking. HairDB also applied an artificial intelligence-enabled search to discover organic aerosol biomarkers in literature. A set of 768 chemicals used in hair-related products was then curated through a combination of manual searches and data extraction from the Cosmetic Ingredient Database (CosIng) of the European Union. From manually reading review papers, 29 organic aerosol biomarkers were extracted. Furthermore, 3,679 known exposure chemicals extracted from the Toxin and Toxin Target Database (T3DB) were incorporated in HairDB to represent the possible environmental exposures detected on hair surfaces. The comprehensive set of chemicals captured in HairDB represents the current knowledge of what can be found in and on hair. HairDB was constructed as a user-friendly web interface, allowing easy exploration of hair-related chemicals and tailored for annotating mass spectrometry-based hair exposomics data. The development of HairDB marks an important step forward in using hair as a biological matrix for chemical exposure measurement, facilitating the adoption of hair for exposome research. HairDB is publicly available at https://www.hairdb.ca/.

Post mortem chiral analysis of MDMA and MDA in human blood and hair

Drug-related fatalities in the EU are predominantly associated with opioids. MDMA (Ecstasy) consumption results in fewer lethal intoxications despite its widespread use. This study investigates MDMA-related fatalities, focusing on enantiomer ratios of MDMA and its metabolite MDA to explore the role of metabolism in fatal outcomes.MDMA induces euphoria, increased empathy, and physiological effects such as tachycardia, hypertension, and hyperthermia. Metabolism mainly involves CYP1A2 and CYP2D6, with polymorphism of the latter influencing metabolism rates. Our institute observed several MDMA-related fatalities, which prompted an investigation into the potential role of inefficient drug metabolism in these cases.A novel quantitative chiral analysis method was developed and validated for MDMA, MDA, amphetamine and methamphetamine enantiomers in human blood. Analysis of post mortem blood samples from eleven MDMA-related fatalities exhibited a wide range of concentrations and enantiomer ratios. Variability in R/S MDMA ratios, however, could be linked to the time period of metabolism. Hair analysis revealed high MDMA concentrations in all segments, irrespective of prior drug abuse anamnesis. Therefore, hair analysis may not be suitable for the assessment of past drug use in ecstasy-related fatalities.The results indicated that elevated levels of the MDMA enantiomer are correlated with longer survival times in cases of intoxication. However, there was no clear evidence for slowed MDMA metabolism as a cause of lethal intoxications. While challenges remain due to the diversity of cases, this study contributes valuable insights into ecstasy intoxications, aiding future interpretation of post mortem analysis.

Concurrent genotyping of mitochondrial DNA and nuclear DNA in rootless hair shafts and blood samples for enhanced analysis

Concurrent genotyping of mitochondrial DNA and nuclear DNA in rootless hair shafts and blood samples for enhanced analysis

Inhibiting dipeptidyl peptidase 4 positive fibroblasts using zinc sulfide cellulose nanofiber scaffolds to achieve scarless healing

Wound regeneration with integral function and cutaneous appendages remains challenging in wound dressing applications. Cellulose nanofibers (CNF) exhibit remarkable characteristics in wound dressing applications; however, their utility in the wound healing process is limited by insufficient scar inhibition and regenerative healing. Herein, inspired by fibroblast heterogeneity mediating wound healing and skin regeneration, we developed a CNF scaffold designed to block Dipeptidyl Peptidase 4 positive (DPP4+) fibroblasts for regenerative healing. CNF encapsulated sitagliptin (SITA) and zinc sulfide nanoparticles (NZnS), namely CNF@SITA@NZnS, to fabricate a novel biomaterial for scar reduction and regenerative healing. The scaffold promoted scarless healing and hair follicle regeneration in rats. In vivo experiments, the wounds in the scaffold showed less skin fibrosis, a better collagen ratio and more new hair follicles. In vitro experiments showed that the scaffold material promoted scarless healing, possibly by inhibiting the secretion of extracellular matrix and fibroblast-to-myofibroblast conversion. The promotion of hair follicle regeneration by the scaffold material may be due to promotion of the migration and proliferation of human hair follicle papilla cells. RNA sequencing is performed to explore the underlying mechanisms, which can activate ECM-receptor interaction pathway in favor of the wound healing process. The inhibiting effect of CNF@SITA@NZnS scaffold on DPP4+ fibroblasts can be a potential target to reduce scarring and promote skin regeneration.

Comparison of In Vitro Hair Growth Promotion and Anti-Hair Loss Potential of Thai Rice By-Product from Oryza sativa L. cv. Buebang 3 CMU and Sanpatong.

The bioactive compounds in herbal extracts may provide effective hair loss treatments with fewer side effects compared to synthetic medicines. This study evaluated the effects of Buebang 3 CMU and Sanpatong rice bran extracts, macerated with dichloromethane or 95% ethanol, on hair growth promotion and hair loss prevention. Overall, Buebang 3 CMU extracts contained significantly higher levels of bioactive compounds, including γ-oryzanol, tocopherols, and various polyphenols such as phytic acid, ferulic acid, and chlorogenic acid, compared to Sanpatong extracts. Additionally, ethanolic extracts demonstrated greater bioactive content and antioxidant activities than those extracted with dichloromethane. These compounds enhanced the proliferation of human hair follicle dermal papilla cells (HFDPCs) by 124.28 ± 1.08% (p < 0.05) and modulated anti-inflammatory pathways by reducing nitrite production to 3.20 ± 0.36 µM (p < 0.05). Key hair growth signaling pathways, including Wnt/β-catenin (CTNNB1), Sonic Hedgehog (SHH, SMO, GLI1), and vascular endothelial growth factor (VEGF), were activated by approximately 1.5-fold to 2.5-fold compared to minoxidil. Also, in both human prostate cancer (DU-145) and HFDPC cells, the ethanolic Buebang 3 CMU extract (Et-BB3-CMU) suppressed SRD5A1, SRD5A2, and SRD5A3 expression-key pathways in hair loss-by 2-fold and 1.5-fold more than minoxidil and finasteride, respectively. These findings suggest that Et-BB3-CMU holds promise for promoting hair growth and preventing hair loss.

Rapid and Effective Determination of Ethyl Glucuronide in Hair by Micro Extraction by Packed Sorbent (MEPS) and LC-MS/MS.

Ethyl glucuronide (EtG) in hair is a reliable biomarker of alcohol consumption habits. Due to its small concentration incorporated into hair, analytical methods sensitive enough to reliably quantify EtG in this matrix are required. Sample preparation is critical in hair analysis, especially for EtG, for which extraction efficiency and matrix effect can strongly influence the results; furthermore, miniaturized methods are sought, to reduce solvent use and times of sample preparation. A micro extraction by packed sorbent (MEPS) procedure coupled to a high-performance liquid chromatography-tandem mass spectrometry method was developed and validated for quantitation of EtG in human hair samples. Fifty milligrams of hair samples were cut into snippets and extracted in water. The cleanup of the extract was carried out by using a MEPS syringe packed with anion exchange sorbent (SAX); all parameters for conditioning, washing, loading and eluting steps were optimized and the eluted aqueous volume was directly injected in the LC-MS/MS system operating in the negative ionization mode. The method was fully validated assessing LOD, LOQ, calibration curve, repeatability, accuracy, matrix effect and carryover. The method was subsequently applied to QCs and authentic hair samples. The developed MEPS method is quick and effective, with low solvent purchase and discard costs, allowing the differentiation between social drinkers and chronic excessive alcohol consumers, according to the cut-offs established by the Society of Hair Testing (SoHT).

Assessing the Arsenic Contents and Associated Risks in Groundwater of Vehari and Lodhran Districts, Pakistan

Exposure to arsenic (As) can induce numerous lethal diseases, such as cancer, cardiovascular issues, skin diseases, and diabetes in humans. The major route of human and animal exposure to As is through drinking As-rich groundwater. This study assessed As occurrence in the groundwater of two districts in the Punjab (Vehari and Lodhran) provinces of Pakistan. Groundwater analysis revealed an average As concentration of 7.7 µg/L (n = 79) in the study area, with a maximum As concentration up to 41.4 µg/L (33% of samples exceeding the WHO limit of 10 µg/L). Arsenic traces were found in animal milk (n = 15, mean: 0.79 µg/L, 17% exceeding 2.0 µg/L), human hair (n = 12, mean: 0.36 µg/g, 17% exceeding 1.0 µg/g), and human nails (n = 8, mean: 0.03 µg/g, none of the samples exceeded 1.0 µg/g). Health risk assessment indices revealed that about 33% of the hazard quotient and 54% of the cancer risk factor exceeded their thresholds. Despite the low–moderate As concentration in groundwater and the accumulation of As in a few biological samples, there is a possibility of potential As poisoning via the long-term and continuous use of groundwater for drinking. Monitoring and blanket testing of wells for As in well water can provide baseline data to minimize the threat of As-mediated arsenicosis in As-affected areas of Pakistan. Moreover, a detailed study of potential As accumulation in biological samples with a higher number of samples is recommended in the area.

The Genomic Variation in Textured Hair: Implications in Developing a Holistic Hair Care Routine

Human hair is characterised by variability, determined by genetic and macromolecular factors. Whilst the European hair type has been a focus of extensive research, Afro-textured hair care faces challenges created by insufficient knowledge of its properties. Applications of hair care products that are incompatible with Afro-textured hair frequently have detrimental effects on the scalp. This highlights the need for partnerships to bridge the gap between research and hair care practices and address challenges related to Afro-textured hair. In this review, we performed data mining of the existing literature and in silico network analysis of the biomarkers relevant to Afro-textured hair. The approaches to hair maintenance are highlighted in the context of hair anatomy and growth cycles, organisation of keratins, surface lipids, and chemical bonds. We discuss a range of biomarkers affecting hair fibre’s shape and mechanical strength, with the gene interactive network pointing to the hierarchical organisation of important traits, notably hair shaft diameter, keratinization, and hair follicle patterning, which likely contribute to the increased sensitivity of hair to extrinsic factors. We propose that a better understanding of the genetic traits, molecular structure, and biomechanics of Afro-textured hair is required to initiate more effective hair care solutions that would benefit the wider population.

James Hutton and the measurement of atmospheric moisture

Measuring the amount of water in the air has been one of the most challenging of routine tasks in meteorology. From the 1650s onwards the methods involved either the uptake of moisture by organic materials such as human hair and whalebone (hygrometry) or the measurement of cooling due to loss of latent heat during evaporation (psychrometry). In 1792 James Hutton reported that a thermometer previously moistened by water records a lower temperature when exposed to cooling in the wind. This led to the development of the first condensation hygrometer by John Leslie in 1801 based on wet- and dry-bulb thermometers, whose design was refined and improved throughout the nineteenth century. Determining relative and absolute humidity values from a hygrometer required the use of a psychrometric equation, first developed by James Ivory in 1822 and later refined by Ernst Ferdinand August, James Apjohn and many others. Modern-day determinations of humidity often involve an aspirated psychrometer located in a Stevenson screen, whose origin can be traced directly back to Hutton’s observation of cooling due to evaporation. An extensive review of the literature on psychrometry records only cursory and ill informed acknowledgement of Hutton’s contribution. This article reasserts Hutton’s seminal role in the history of psychrometry.

Dermal Papilla Cells: From Basic Research to Translational Applications.

As an appendage of the skin, hair protects against ultraviolet radiation and mechanical damage and regulates body temperature. It also reflects an individual's health status and serves as an important method of expressing personality. Hair loss and graying are significant psychosocial burdens for many people. Hair is produced from hair follicles, which are exclusively controlled by the dermal papilla (DP) at their base. The dermal papilla cells (DPCs) comprise a cluster of specialized mesenchymal cells that induce the formation of hair follicles during early embryonic development through interaction with epithelial precursor cells. They continue to regulate the growth cycle, color, size, and type of hair after the hair follicle matures by secreting various factors. DPCs possess stem cell characteristics and can be cultured and expanded in vitro. DPCs express numerous stemness-related factors, enabling them to be reprogrammed into induced pluripotent stem cells (iPSCs) using only two, or even one, Yamanaka factor. DPCs are an important source of skin-derived precursors (SKPs). When combined with epithelial stem cells, they can reconstitute skin and hair follicles, participating in the regeneration of the dermis, including the DP and dermal sheath. When implanted between the epidermis and dermis, DPCs can induce the formation of new hair follicles on hairless skin. Subcutaneous injection of DPCs and their exosomes can promote hair growth. This review summarizes the in vivo functions of the DP; highlights the potential of DPCs in cell therapy, particularly for the treatment of hair loss; and discusses the challenges and recent advances in the field, from basic research to translational applications.

Multifunctional Carbon Dots Derived from Human Hair for Fast Healing Wounds Together with Oleogels

In the complex process of wound healing, oleogels (OG) are suitable as the primary component of dressing materials, but they cannot meet the diverse requirements at different healing stages. In this study, a new kind of carbon dots (CrCi‐CDs) prepared by carbonizing human hair, exhibits excellent hemostatic, antibacterial, anti‐inflammatory, and pro‐angiogenic properties and thus supports the various stages of wound healing effectively. Such CrCi‐CDs are incorporated into OG to produce a CrCi‐CD/OG composite material with enhanced multifunctional capabilities, significantly outperforming OG alone. Various experiments in vitro and in vivo confirm that the CrCi‐CDs/OG can rapidly achieve hemostasis at the initial stage of wound formation, subsequently inhibit bacterial proliferation and biofilm formation, improve the complex microenvironment surrounding the wound, and promote neovascularization, ultimately accelerating the wound repair.

Occupational exposure assessment of heavy metals in human scalp hair among tannery workers in Bahir Dar, Ethiopia: Indication of pollution

Ethiopia, is one of the African countries, has immense potential for skins and hides for the leather industries, which will play a crucial role in converting nations into manufacturing-driven economies through industrialization. The chemicals applied in the tanning process are a serious concern for employees and the community if proper safety measures are not taken. The pollution status of employees working in Anbessa and Bahir Dar tannery factories was evaluated by collecting hair samples. After the hair samples washed with acetone, and deionized water, the hair samples were digested with 4 mL of HNO3 and 2 mL of HClO4 for 1:30 h at 250 °C. The levels of metals (Cr, Pb, Zn, Cu, Ni, and Cd) were subsequently analyzed using a Flame Atomic Absorption Spectrophotometer (FAAS). The mean concentrations of Cu, Ni, Zn, Pb, and Cr in the Anbessa tannery factory workers were 17.34–22.75, 16.38–35.03, 235.4–369.2, 30.46–67.31, and 97.56–189.18, respectively, in the various working departments of the factory. Similarly, the concentrations of Cu, Ni, Zn, Cd, Pb, and Cr in the hair of Bahir Dar tannery workers were 30.1–105.9, 17.88–62.20, 216.9–762.1, 0.35–5.21, 33.42–91.42, and 118.5–305.7, respectively. Chromium was found to be the most accumulated metal next to Zn with in both tannery workers that highlighted significant occupational health risks. The principal component analysis (PCA) analysis provide an insights into the interactions between occupational factors and metal exposure. In conclusion, the results of hair analysis from the employees of tannery factories indicates alarming levels of metal exposure, especially for zinc and chromium, which might pose health problems in long time exposure. Thus, it's critical to monitor occupational activities that can harm human health and the environment.