Celebrating the End of Another Cycle of Seasonal Shedding

October is the Start of Progressively Less Daily Hair Shedding

In the northern hemisphere, October marks the end of another cycle of seasonal hair shedding. If you are looking for a reason to celebrate, this one can be added to the list.

Seasonal shedding is common in humans and refers to the cyclic variation in daily hair shedding patterns in different seasons. Shedding is highest in Spring and again in late Summer/early Fall (Autumn) and lowest in winter.  For those living in the Northern hemisphere, this means that the month October marks the transition from high shedding rates to progressively lower rates. Everything gets better and better from October onwards.

October marks an important transition whereby humans experience progressively less daily shedding until the next spring and summer.

The Key Seasonal Hair Shedding Studies

In 1991,  Randall and Ebling studied the hair growth parameters every 28 days of 14 healthy males.  The authors found that the proportion of hairs in anagen (by pluck tests) reached peak in March each year and then fell steadily through September. This findings was true for all areas of the scalp studied including the vertex parietal and occipital areas of the scalp. When the authors examined the bags of hair that were collected from participants, they found that shed hair was maximal in August and September and least in March. 

 In 1996, Courtois et al studied 10 subjects over a period of 8 to 14 years.   The authors found that late summer and early Autumn (August, September and October) were periods of the highest telogen percentages and December January and February were the periods of minimal shedding. The authors identified a smaller peak of shedding in Feb and March. 

In 1999, Pierard-Franchimont and Pierard performed trichograms of 2857 subjects over 2 consecutive years. They found an increased proportion of telogen effluvium between July and October. The lowest rates were found in January. 

In 2008, study from  Switzerland examined shedding patterns in 823 women using trichograms. The authors found that telogen rates were lowest at the beginning of February and highest in July. There was a second peak noted by the authors in April  it was less pronounced than in summer.  The authors showed that this seasonal shedding occurred regardless of whether or not the patient had female pattern hair loss and regardless of whether or not they were using minoxidil. 

In 2014, Liu et al, 2014 studied seasonal changes in hair growth patterns in 41  male and female volunteers from China. Phototrichograms were used to record the percentage of hairs in anagen and telogen. The authors showed that the highest proportion of telogen hairs were in September and lowest in January. In women, these proportions rose formapproximately 8 % in January to 12 % in September. 

Conclusion

Seasonal shedding is frustrating. Many patients experience increased shedding in August and September. The arrival of the month of October is very much a welcome relief as it marks a steady reduction in shedding. Seasonal shedding is critically important for hair specialists to recognize so as to not false attribute the cause of a person’s hair shedding to another (potentially incorrect) cause.

References

Courtois et al.Periodicity in the growth and shedding of hair. Br J Dermatol, 1996 Jan;134(1):47-54.

Hsiang EY et al. Seasonality of hair loss: a time series analysis of Google Trends data 2004-2016. Br J Dermatol2018; 178(4):978-79   

Liu et al. A Microarray-Based Analysis Reveals that a Short Photoperiod Promotes Hair Growth in the Arbas Cashmere Goat, PLoS One. 2016 Jan 27;11(1):e0147124.  

Maurel D et al. Effects of photoperiod, melatonin implants and castration on molting and on plasma thyroxine, testosterone and prolactin levels in the European badger (Meles meles). Comp Biochem Phyiol A Comp Physiol. 1989;93(4):791-7.

Orentreich N. Scalp hair replacement in man. In: Advances in Biology of Skin. Vol IX: Hair Growth. (Montagna W, Dobson RI, eds). Oxford: Pergamon. 1969. 99-108.

Pearson AJ et al. Inhibitory effect of increased photoperiod on wool follicle growth. J Endocrinol 1996 Jan;148(1):157-66.

Piérard-Franchimont C, Peérard GE .L'effluvium télogène actinique: une facette de la chronobiologie humaine.

Int J Cosmet Sci. 1999 Feb;21(1):15-21.

Randall and Ebling. Seasonal changes in human hair growth. Br J Dermatol 1991.

Reinberg A et al. Circadian and circannual rhythms in plasma hormones and other variables in five healthy young males. Acta Endocrinology 1978; 88: 417-27

Smals AGH et al. Circannual cycle in plasma testosterone levesl in man. J Clin Endocrin Metab 1976; 42: 979-82.

Zhang et al. Comparative study on seasonal hair follicle cycling by analysis of the transcriptomes from cashmere and milk goats. Genomics 2019 Feb 16