Scientists from L’Oréal Research & Innovation and Queen Mary University of London report that human hair is not pushed out from the follicle by dividing cells in the hair bulb, as traditionally taught.  

Instead, growth is driven by an upward pulling force generated by coordinated movement of cells in the outer layers of the hair follicle.  

Using advanced three-dimensional live imaging of human hair follicles kept alive in culture, the researchers tracked individual cell movements over time. They observed that cells in the outer root sheath – the layer of tissue encasing the hair shaft – move in a downward spiral deep within the follicle. This organised motion appears to create a pulling mechanism that draws the hair upward through the skin.   

To test the mechanism, the team experimented with inhibiting key cellular processes. Blocking cell division in the hair bulb slowed hair growth only moderately, suggesting that traditional “push” forces were not the primary driver. In contrast, disrupting the cytoskeleton – the structural network that enables cell movement – greatly reduced hair growth, supporting the idea that collective cell motion generates the pulling force.   

These findings revise a core concept of hair biology and may have implications for understanding hair loss and regeneration. If hair growth depends on dynamic cellular movements rather than solely on proliferation at the base of the follicle, this could influence how scientists approach therapies for conditions such as androgenetic alopecia or other forms of hair thinning. Further research will be needed to connect these mechanical insights with clinical strategies for enhancing hair regeneration.