Alopecia: what it is, what types exist and how to recognize them

What is alopecia?

If we look up what alopecia is, the simplest definition is the loss of hair in an area where it would normally be present.

But alopecia is not a single diagnosis.

It is a term that encompasses numerous different diseases and mechanisms.

And this distinction has very important consequences: the treatment that may work for androgenetic alopecia does not necessarily work for alopecia areata, and neither of these conditions is managed in the same way as scarring alopecia.

Hair loss and alopecia: are they the same thing?

Not exactly.

We can experience significant hair shedding for several months without developing permanent hair loss.

This occurs, for example, in certain cases of telogen effluvium.

The opposite can also happen: a person may not notice large amounts of hair falling out in the shower and yet be progressively losing density because their follicles are producing increasingly finer hairs.

This is characteristically seen in androgenetic alopecia.

That is why the amount of hair we find in the brush does not always reflect what is actually happening at the follicle.

What are the main types of alopecia?

A particularly important classification involves distinguishing between non-scarring alopecias and scarring alopecias.

The difference is fundamental.

In the former, the follicle remains potentially functional.

In scarring alopecias, on the other hand, the inflammatory process can destroy the follicle and replace it with scar tissue. When a follicle has been permanently destroyed, recovering that hair becomes much more difficult or impossible.

Let us look at some of the most important forms.

1. Androgenetic alopecia

Androgenetic alopecia is one of the most common causes of progressive hair loss.

It can affect both men and women.

There is a genetic predisposition, and certain follicles display a particular sensitivity to androgens.

Over time, a phenomenon known as follicular miniaturization occurs.

The follicle continues to produce hair, but each new hair can progressively become finer, shorter, and less visible.

How can we recognize it?

In men, a progressive recession of the frontal hairline, temples, and loss of density at the top or crown may appear.

In women, a progressive decrease in density and a widening of the central parting is frequently observed.

Hair loss in women deserves a specific evaluation because other mechanisms of hair loss may coexist.

Furthermore, diagnosing it early is important: while the follicle remains active, we have greater therapeutic possibilities than when miniaturization is very advanced.

2. Alopecia areata

Alopecia areata is completely different.

It is an autoimmune disease in which the immune system affects the hair follicle.

Its classic presentation consists of the relatively rapid appearance of one or more rounded or oval areas without hair.

The skin may appear apparently normal.

But there are far more extensive forms.

When all the hair on the scalp is lost, we speak of alopecia totalis, and when the loss affects virtually all body hair, we speak of alopecia universalis.

Therefore, we must not confuse a patch that appears suddenly without hair with the progressive loss of density typical of androgenetic alopecia.

3. Telogen effluvium

Telogen effluvium is a common cause of diffuse hair loss.

Here, many follicles shift in a relatively synchronized manner toward a phase of the cycle that will ultimately result in hair shedding.

It can appear following certain triggers: illnesses, fever, surgical procedures, childbirth, significant weight loss, certain nutritional restrictions, some medications, or situations of physiological stress.

An important characteristic is that the triggering episode may have occurred several months before the patient begins to notice the hair loss.

That is why the connection is often not made at first.

Unlike certain scarring alopecias, the follicle is not necessarily destroyed, and many forms can recover once the trigger has been corrected or has disappeared.

4. Traction alopecia

Traction alopecia occurs when certain hairstyles produce repeated tension on the follicles.

Very tight ponytails, braids, extensions, or other hairstyles maintained over prolonged periods can contribute to its development.

Initially it may be reversible if the traction is eliminated.

But if this aggression persists for a long time, it can end up causing permanent damage to the follicle.

This is an excellent example of why identifying the type of alopecia early can change the prognosis.

5. Frontal fibrosing alopecia

Frontal fibrosing alopecia deserves special attention because it belongs to the group of scarring alopecias.

It frequently affects women, especially after menopause, though not exclusively.

It can cause a progressive recession of the frontal and temporal hairline and be associated with loss of the eyebrows.

Here the therapeutic goal is fundamentally to stop or slow the progression of the disease before it continues destroying follicles.

That is why we should not automatically interpret a recession of the frontal hairline as androgenetic alopecia.

How do we know what type of alopecia we have?

We cannot determine this simply by counting how many hairs appear in the shower.

The diagnosis begins with the clinical history.

How did it start? Was it sudden or gradual? Is there shedding, or is it primarily a loss of density? Is there a family history? Has there been an illness, surgery, childbirth, weight loss, or new medications? Is there itching, pain, scaling, or inflammation?

Then we examine the scalp.

Trichoscopy: looking at the follicle in a different way

One of the most useful tools in hair dermatology is trichoscopy.

Using a magnification system, we can observe structures of the hair and scalp that cannot be adequately assessed with the naked eye.

We can study, among other characteristics, variations in hair shaft diameter, follicular distribution, inflammatory signs, and other patterns that help guide the diagnosis.

In many patients, combining the clinical history, physical examination, and trichoscopy makes it possible to differentiate the main types of alopecia.

Do we always need blood tests?

No.

This is another important concept.

There is no such thing as a 'universal alopecia blood panel' that we should routinely order for every patient.

When the clinical history raises suspicion of certain causes, we can investigate, for example, iron metabolism, thyroid function, or other parameters selected according to the clinical context.

In certain women, there may also be circumstances that justify a hormonal workup.

But tests must answer a clinical question.

When do we need a biopsy?

In the majority of patients, it is not necessary.

However, when diagnostic uncertainty exists or we suspect certain scarring alopecias, a scalp biopsy can provide very important information.

This is especially relevant because distinguishing a scarring alopecia from a non-scarring one can completely change our therapeutic goals.

Can all alopecias be treated?

Many have available treatments, but the goal is not always the same.

In androgenetic alopecia, we can aim to preserve existing follicles, slow progression, and improve density.

In telogen effluvium, our primary goal is to identify and correct the trigger when one exists.

In alopecia areata, we must address the immunological process.

And in scarring alopecia, our priority may be to stop the inflammation in order to prevent it from continuing to destroy follicles.

That is why simply speaking of 'anti-hair loss treatment' is medically far too imprecise.

What about minoxidil?

Minoxidil is one of the best-known treatments in hair medicine and can be very useful in certain patients.

However, as we explained in another article in El médico te explica, it is not the treatment for all types of alopecia.

It can play an important role in androgenetic alopecia and be used in certain additional contexts, but its indication depends on the diagnosis.

Applying minoxidil without knowing what type of alopecia we have is not a substitute for a medical evaluation.

So, how can I recognise my type of alopecia?

We can gather some clues:

A progressive loss of density over years may lead us to think of androgenetic alopecia.

One or more patches that appear suddenly without hair may point towards alopecia areata.

Heavy, diffuse hair loss that begins months after a significant event may be consistent with telogen effluvium.

A progressive frontal recession accompanied by loss of eyebrows may lead us to consider frontal fibrosing alopecia.

And localised loss in areas that are continuously subjected to tension may suggest traction alopecia.

But these clues are no substitute for a diagnosis.

Different conditions can look alike, especially in their early stages.

What I want you to remember

When someone says 'I have alopecia,' the next question should be: 'Which type of alopecia?'

Because there are many types of alopecia, and they do not share the same cause, the same prognosis, or the same treatment.

Some are reversible. Others require ongoing treatment. And some must be diagnosed quickly, because they can permanently destroy the hair follicle.

That is why, in hair medicine, naming the problem is not a minor detail. It is what determines what we need to do next.