Hair loss in autumn

Learn about the causes of hair loss in autumn, its relationship with telogen effluvium and why it is important to address it when it occurs in women with a history of androgenetic alopecia.

Increased hair shedding during autumn is very common and can be a significant cause of concern for many patients. In most cases, it corresponds to telogen effluvium, resulting from the effect of seasonal variations on the hair growth cycle.

Hair growth and shedding cycle

It is important first to understand how the hair follicle growth cycle works.

The hair follicle undergoes continuous changes throughout its growth cycle, which consists of the following stages: the growth phase (anagen), the regression phase (catagen) and the resting phase (telogen), which ends with hair shedding (teloptosis). This cycle of growth and regeneration continues throughout life. The duration of the anagen phase determines the length and diameter of the hair.

There are substantial variations in the duration of these phases depending on the area of the body and between individuals. On average, the anagen phase lasts between two and six years, while the telogen phase lasts approximately 100 days. Under normal conditions, the ratio of scalp hairs in anagen to those in telogen is approximately 9:1.

Each follicle has its own mechanisms for regulating progression through and activation of the different phases of the growth cycle. However, certain systemic factors — including hormones and growth factors — as well as external influences such as environmental factors, toxins and nutritional or vitamin deficiencies can affect the hair growth cycle and trigger telogen effluvium, one of the most common causes of diffuse hair shedding.

Telogen effluvium involves an increase in the proportion of hair follicles entering the telogen, or resting, phase, followed by increased shedding of these hairs (teloptosis) and the subsequent start of a new active growth phase (anagen).

In practical terms, a larger proportion of hairs enter the telogen phase at the same time as a result of synchronisation of the follicles. Once this period ends, a greater number of hairs are shed simultaneously, which may explain the increased hair loss seen in autumn.

Why does hair loss increase in autumn?

Several studies have identified a seasonal pattern in the hair growth cycle, with an increase in the number of hairs entering the telogen phase in July. Given that this phase lasts approximately 100 days, increased hair shedding — or teloptosis — may therefore be observed during autumn.

A second, less pronounced peak appears to occur around April, followed by increased hair shedding in June and July. One hypothesis is that this phenomenon may be triggered by the rise in environmental temperature that occurs at that time of year.

Clinical features, causes and progression of telogen effluvium

Telogen effluvium is a non-scarring form of hair loss characterised by diffuse shedding without clearly defined areas of complete hair loss and generally has an acute onset. A chronic form also exists, with a more gradual onset and longer duration, and this is more common in women.

As mentioned above, telogen effluvium may occur as a reactive process in response to seasonal changes, metabolic stress, hormonal alterations, medication, nutritional deficiencies, childbirth, vaccinations or inflammatory scalp conditions, among other factors.

It can affect hair throughout the body, although shedding from the scalp is usually the most noticeable and potentially concerning manifestation.

Diagnosis is primarily clinical and may be supported by trichoscopy and/or trichogram assessment. As scalp hair grows at an approximately constant rate of around 1 cm per month, the duration of the shedding process can sometimes be estimated by measuring the length of short regrowing hairs using trichoscopy. A comprehensive blood test is also generally recommended to rule out potential underlying causes of telogen effluvium. If an abnormality is identified, it should be treated appropriately.

In most cases, recovery occurs spontaneously within six months of onset. However, if there is an underlying form of alopecia, the condition may become chronic. In these situations, assessment by a dermatologist specialised in telogen effluvium is advisable.

Telogen effluvium is relatively common, although its exact prevalence is not known. Most adults experience at least one episode during their lifetime, which should be taken into consideration when assessing increased hair shedding in autumn.

Telogen effluvium and androgenetic alopecia

Women with a history of androgenetic alopecia may experience seasonal telogen effluvium more frequently and more intensely than women without underlying alopecia, which can understandably be a significant source of concern. In these patients, the anagen phase is shorter. As a result, synchronisation of follicles entering the telogen phase may be more marked. In this situation, it is important to treat the underlying androgenetic alopecia appropriately in order to minimise the intensity of the associated telogen effluvium.

Post updated. First version published on 22 October 2022.

We invite you to share this article about hair loss in autumn with family and friends who may find it useful.