TLDR The hair cuticle is made of tough proteins that protect the hair, but more research is needed to fully understand its structure.
The review from May 2019 discussed the structure and function of the hair cuticle, emphasizing its protective role for the inner cortex. It detailed the three layers of the cuticle—A-layer, exocuticle, and endocuticle—and their distinct properties, including high disulphide crosslinking for toughness and the hydrophobic nature due to 18-methyleicosanoic acid (18-MEA). Despite extensive research, some aspects of cuticle structure and development remained unclear, highlighting the need for innovative techniques like TEM autoradiography to study these areas. The review underscored the importance of further research to improve understanding and treatment of hair.
90 citations,
January 1979 in “International review of cytology” Wool follicles are complex, involving interactions between different cell types and structures.
138 citations,
November 1977 in “Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics” 82 citations,
November 1959 in “Annals of the New York Academy of Sciences” 
191 citations,
November 1959 in “Annals of the New York Academy of Sciences” Hair and wool have complex microscopic structures with microfibrils and varying cystine content.
34 citations,
July 1958 in “Biochimica et Biophysica Acta”
Human hair keratins can self-assemble and support cell growth, useful for biomedical applications.
5 citations,
February 2022 in “Acta Biomaterialia” Nanomaterials can improve hair care products and treatments, including hair loss and alopecia, by enhancing stability and safety, and allowing controlled release of compounds, but their safety in cosmetics needs more understanding.
19 citations,
January 2009 in “International review of cell and molecular biology” Hair's strength and flexibility come from its protein structure and molecular interactions.
47 citations,
January 2017 in “RSC Advances” Keratin peptides can change hair shape gently without harsh chemicals.
October 2024 in “Cosmetics” Afro-textured hair needs personalized care due to its unique genetic traits.
