The Seasonality of Hair Shedding

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The Seasonality of Hair Shedding

As the Autumn in Toronto transitions from summer to early autumn approaches, I'm reminded of a remarkable feature of human hair growth - the increased tendancy for humans to shed hair in the early Fall.

Several research studies have shown that humans living in northern regions tend to shed more during the late summer and early autumn months.   Most of the time this goes undetected, but some individuals do notice this feature. A second phase of increase shedding in human beings may occur in Spring as well.

What causes hair shedding?

Of course, anyone coming into the office with concerns about hair shedding requires a thorough evaluation to determine the causes of increased hair shedding. These many include:

Physiological stress (i.e. surgery, labour and delivery, systemic diseases of the body, infections)

Endocrine problems (i.e. thyroid abnormalities)

Nutritional deficiencies (i.e. low iron, dieting)

Medications (i.e. anti-depressants, ACE inhibitors, heparin, beta blockers, lithium)

In addition to a thorough history and scalp examination, a patient with concerns about hair shedding requires blood work for complete blood count, thyroid studies and iron studies. Other studies may be needed as well.  All in all, there is a periodicity to how humans normally shed hair. Although loss of 50-100 hairs each and every day is considered normal, slightly increased rates can be observed in the Fall.

References of Interest

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

2) Kunz M et al. Seasonality of hair shedding in healthy women complaining of hair loss. Dermatology 2009; 219: 105-10.

3) Randall CA and Ebling EJG. Seasonal changes in human hair growth.  Br J Dermatol 1991; 124: 146-51.



Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss. To schedule a consultation, please call the Whistler office at 604.283.1887

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