TLDR Hair ages as the cuticle wears down, especially beyond 1 meter from the root, affecting its strength and shine.
The study examined very long human hair (over 2.4 meters) to understand the natural aging process of hair keratin fibers using various evaluation methods. It found that hair aging begins with the progressive abrasion of the cuticle while the cortex remains unchanged up to about 1 meter from the root, maintaining shine, hydrophobicity, and friction characteristics. Beyond this point, significant cuticle damage occurs, correlating with a decline in ceramides, 18-Methyl Eicosanoic Acid (18-MEA), and keratin-associated protein content. This leads to a noticeable decay in the mechanical and optical properties of the hair. The research provided a detailed time-dependent 'damage scale' of human hair, which could aid in developing new hair care products.
115 citations,
September 2005 in “International Journal of Dermatology” Different ethnic groups have unique hair growth patterns, with African hair growing slower and less dense, Asian hair growing fast but sparse, and Caucasian hair being densest; men are more likely to experience hair loss than women.
41 citations,
May 2005 in “International Journal of Cosmetic Science” Human hair contains various lipids that vary among individuals and help protect the hair.
15 citations,
October 2004 in “Colloids and surfaces. B, Biointerfaces” Holes in mature hair are likely caused by the removal of substances during hair care.
22 citations,
February 2002 in “Journal of theoretical biology” The model showed that randomness accurately describes individual hair growth cycles and that synchronization can cause large fluctuations not seen in humans.
1 citations,
May 2023 in “Frontiers in medicine” Hair dyes and perms can damage hair and scalp, but using interventions can reduce harm.
September 2017 in “Journal of Investigative Dermatology” Hair care products used for 4 weeks made hair smoother.
25 citations,
August 2015 in “Journal of cosmetic dermatology” African American women report more hair issues and use different hair care practices than Caucasian women, and have different hair and scalp characteristics.
7 citations,
August 2006 in “Biopolymers” Researchers extracted tiny keratin filaments from human hair by unzipping its outer layer.
71 citations,
August 2005 in “The journal of investigative dermatology. Symposium proceedings/The Journal of investigative dermatology symposium proceedings” Hair keratin-associated proteins are essential for strong hair, with over 80 genes showing specific patterns and variations among people.
