Hair growth is a cyclical process consisting of four main phases: the growth phase, the transitional phase, the resting phase and the shedding phase. Hair follicles reach their peak growth in spring, before slowing down in autumn, which explains the increased hair loss during this period. During the summer months, the majority of hair strands enter the resting phase, which means that in autumn, particularly in October and November, more hair falls out. This phenomenon can also be traced back to evolutionary causes, as our ancestors’ coat change was synchronised with the seasons.
In addition, the summer heat, increased sunlight and hormonal changes – such as reduced thyroid activity – can also contribute to autumn hair loss. What’s more, as the days get shorter in autumn and we receive less natural light, our circadian rhythm – that is, the rhythm of our internal biological clock – can become disrupted. This can affect both the quality and quantity of our sleep, which in turn impacts the condition of our hair in several ways: a reduction in the hormone melatonin, produced during sleep, and a rise in stress levels can both affect the condition of our hair.