Telogen effluvium: why hair suddenly falls out

First: how does our hair grow?

To understand telogen effluvium, we must first grasp that our hairs do not grow continuously forever.

Each follicle goes through different phases.

The anagen phase is the active growth phase and can last several years.

Next comes a brief transitional phase called the catagen phase.

Finally, the follicle enters a resting phase called the telogen phase.

After this phase, the hair eventually sheds and the follicle can begin a new cycle.

Normally, our follicles are not all synchronised.

While some hairs are growing, others are resting and others are shedding.

That is why we can lose hair every day without progressively running out of it.

What happens in telogen effluvium?

In telogen effluvium, an event disrupts that balance.

A greater number of follicles than usual shifts into the telogen phase.

But those hairs do not fall out immediately.

They remain in that phase for a period of time and then shed.

This delay explains something that initially seems strange: you may start losing a great deal of hair today because of something that happened approximately two or three months ago.

What can trigger telogen effluvium?

There are numerous possible triggers.

These may include: a significant illness or fever episode, a surgical procedure, childbirth, rapid or substantial weight loss, certain nutritional restrictions, some medications, and various medical conditions.

It can also appear following significant physiological stress.

But there is something we must avoid: automatically attributing any hair loss to emotional stress.

A connection may exist in certain circumstances, but we must first evaluate other causes and the full clinical context.

Why does it start months later?

This is probably the most interesting aspect of telogen effluvium.

Let us imagine that an illness, surgery, or significant weight loss causes numerous follicles to prematurely leave their growth phase.

We will not necessarily see a dramatic shedding at that moment.

Those follicles enter a resting state.

And several weeks later, when the hairs reach the shedding phase, the hair loss appears.

That is why, during the consultation, one of my questions is: 'What happened approximately two or three months before your hair started falling out?'

Very often, that is where we find the clue.

What does the shedding look like?

It is typically a diffuse hair loss.

That is, a single completely bare patch does not necessarily appear, as can happen in alopecia areata.

The patient notices hair loss in different areas of the scalp.

A very typical phrase is: 'Every time I shower, so much hair comes out.' Or: 'I run my hand through my hair and strands are left between my fingers.'

This can cause a great deal of anxiety because the visible amount can be considerable.

Am I going to go bald?

In acute telogen effluvium, usually not.

And this is one of the most important messages for the patient.

The follicle is not necessarily being destroyed.

It has temporarily shifted phase.

When the trigger disappears or we correct it, the cycle can progressively normalize and growth can begin again.

However, this does not mean that we should diagnose any significant hair loss as telogen effluvium without first examining the patient.

How long does it last?

Acute telogen effluvium is usually a self-limiting process.

The shedding can continue for several months before gradually decreasing.

And there is another important detail: the fact that it stops falling does not mean we immediately recover all of our density.

The new hair needs to grow.

Scalp hair grows approximately one centimeter per month, so regaining length and a sense of volume takes time.

Biological improvement begins before we can clearly see it in the mirror.

Is there such a thing as chronic telogen effluvium?

Yes.

When hair loss persists for more than six months, we may be dealing with chronic telogen effluvium.

In these cases it is especially important to review the diagnosis, any persistent triggering factors, and rule out other conditions that may coexist.

Because prolonged hair loss should not automatically become: 'It's stress.'

We need to ask ourselves again what is actually happening.

Telogen effluvium and androgenetic alopecia: can they occur together?

Yes. And this is extremely important.

A person may have early-stage androgenetic alopecia and not yet have noticed it.

Then they develop telogen effluvium.

Suddenly they lose a great deal of hair, and the reduction in density makes the androgenetic alopecia that was already present far more visible.

That is why, after a significant episode of hair loss, some patients say: 'My hair was never the same as before.'

In certain cases, this does not mean that the telogen effluvium has destroyed the follicles.

It may have unmasked another process that was already evolving slowly.

Is hair loss more common in women?

Telogen effluvium is a very common cause of hair loss in women.

There are circumstances that are especially relevant in women, such as the postpartum period, heavy periods with possible iron deficiency, certain diets or weight loss, and thyroid disorders, among others.

But again: being a woman and losing hair does not automatically mean having an iron deficiency or a hormonal problem.

We must look for these abnormalities when the clinical history justifies it.

Telogen effluvium after childbirth

The postpartum period is a classic example.

During pregnancy, hormonal changes alter the hair cycle and many women notice that their hair feels particularly thick.

After childbirth, numerous follicles move in a relatively synchronized manner through the phases that will ultimately lead to their shedding.

A few months later, very noticeable hair loss may appear.

Despite how dramatic it can seem, in the majority of cases there is a progressive recovery.

Can it appear after losing weight?

Yes.

Rapid weight loss and very restrictive diets can trigger telogen effluvium, especially when there is a significant reduction in energy or protein intake, or nutritional deficiencies arise.

This is particularly relevant today because there are multiple pharmacological and dietary strategies capable of producing substantial weight loss over relatively short periods of time.

The follicle is a metabolically active structure.

If we undergo significant weight loss, we must maintain a nutritionally adequate diet.

What about iron?

Iron deserves attention, but also caution.

An iron deficiency can be associated with hair loss and should be corrected when it is present.

But this does not mean that every person experiencing hair loss needs iron supplements.

When the clinical history justifies it, we can assess a complete blood count and parameters of iron metabolism, such as ferritin and other relevant markers.

We then interpret the results in their context.

First we demonstrate the deficit. Then we treat it.

What about the thyroid?

Thyroid disorders can also produce changes in the hair and should be considered when there are symptoms, a relevant medical history, or clinical features that warrant it.

That is why thyroid function may be included in a targeted blood panel in certain patients.

But we do not need to indiscriminately request every hormone test for every person experiencing hair loss.

Do we need blood work?

Not always.

The clinical history is fundamental.

If there is a clear trigger and the physical examination is consistent with it, we can often arrive at a fairly clear picture.

In other cases it may be reasonable to carry out a targeted blood panel to investigate specific causes.

The important thing is that the tests respond to a clinical suspicion — not to order dozens of parameters simply because hair loss is present.

How is it diagnosed?

In addition to the clinical history, we examine the scalp and the distribution of the loss.

Trichoscopy can be particularly helpful in identifying whether follicular miniaturization or other signs suggesting a different type of alopecia are present at the same time.

We also sometimes use clinical tests to assess how active the shedding is.

The primary goal is to confirm that the pattern is consistent and, above all, to make sure we are not overlooking another condition.

Treatment for hair loss in telogen effluvium

Here appears one of the most important concepts in this article.

In many cases, the main treatment for hair loss caused by telogen effluvium consists of: identifying and correcting the trigger whenever possible.

If there is a nutritional deficiency, we correct it.

If there is a medical condition, we treat it.

If a medication may be involved, we assess the clinical situation before making any changes.

And if the trigger has already disappeared, we often need something particularly difficult: time.

Do I need minoxidil?

Not necessarily.

An acute telogen effluvium can resolve spontaneously once the trigger has been addressed.

Minoxidil may be considered in certain contexts, especially when another cause of hair loss such as androgenetic alopecia is present at the same time, but we should not automatically make it the treatment for every case of effluvium.

Again: we treat the patient, not simply the word 'shedding'.

What about vitamins?

Exactly the same principle.

If a deficiency exists, we supplement.

If it does not, taking large amounts of supplements does not necessarily accelerate growth.

Biotin, iron, zinc and other micronutrients have important biological functions.

But an important biological function does not mean that more of them produces more hair.

Should I be worried about the hair I am still losing?

That is understandable.

But there is something I explain to my patients: when the process that triggered the effluvium occurred months ago, the hairs that are currently destined to shed may continue falling out for some time even though the underlying cause has already been corrected.

This explains why the shedding does not necessarily stop the day after the problem is resolved.

The hair cycle needs time to reorganise itself.

When should I seek a consultation?

When the shedding is intense, persists for months, produces a noticeable loss of density, or when no clear trigger can be identified, it deserves a proper evaluation.

We should also seek medical advice if any of the following appear: completely bare patches, scalp inflammation, pain, significant itching, heavy flaking, or loss of eyebrows and eyelashes.

Because these findings may point toward other types of alopecia.

What I want you to remember

Telogen effluvium has a characteristic that explains much of the confusion: what is happening today may be the consequence of something that occurred several months ago.

That is why, when someone comes to my practice worried because they have been losing a great deal of hair for the past three weeks, I do not look only at those three weeks.

I ask what happened before.

Illnesses. Fever. Surgery. Childbirth. Weight loss. Nutritional changes. Medications. And other possible medical conditions.

Because many times the answer is right there.

And above all: a dramatic hair loss episode does not necessarily mean permanent hair loss.

First we identify what is happening. Then we correct what can be corrected. And finally we give the follicle something that is also part of the treatment: time to grow back.