뒷머리 탈모는 왜 잘 안 생길까?後頭部はなぜ薄毛になりにくいのか?Why Does Hair Loss Rarely Happen at the Back of the Head?

And, if hair loss does occur at the back of the head, when and why does it happen?

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When doing hair-loss consultations, there is one question patients ask most often.

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“Why does only the front fall out while the back doesn’t?”

In fact, looking at male-pattern hair loss

the front and crown gradually thin, but the back of the head (occiput) is often maintained relatively long.

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This phenomenon is not mere chance but is deeply related to the embryology of hair and to differences in hormone response.

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Hearing the word embryology feels difficult, right?

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Today I will explain, as simply as possible,

• why the back of the head is less affected by hair loss
• and, even so, when hair loss does occur at the back of the head

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Why does hair loss rarely occur at the back of the head?

First, human hair is formed from the fetal stage.

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The human body develops from largely three tissue layers at the embryonic stage.

• Ectoderm
• Mesoderm
• Endoderm

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Of these, skin, hair, and nails mostly derive from the ectoderm. Why “mostly”? Because the hair of the occiput derives from the endoderm.

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In other words, hair does not simply grow by chance from the skin; it is a structure embryologically programmed from the fetal stage as to where it will differentiate and arise, and depending on where it derives from, its genetic properties and hormone responses can differ.

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This very difference is the core explaining why the back of the head is resistant to hair loss.

The difference between male-pattern hair loss and the back of the head

The most common hair loss is male-pattern hair loss (androgenetic alopecia).

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You have probably often heard that this hair loss

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is influenced by DHT (dihydrotestosterone), one of the male hormones.

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But hair loss does not progress simply because DHT exists, or because there is a lot of it.

Some people’s follicles receive especially negative stimulation from this DHT and gradually become small and weak.

In that process

• the follicles gradually shrink
• the hair gradually thins
• and finally turns downy.
• The growth phase shortens and the resting phase lengthens
• and resting follicles increase too.

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This is called follicle miniaturization, the “vellus transformation” process.

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The problem is that this reaction does not occur identically across the whole scalp.

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As said above, because the origin differs

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the follicles of the front and crown

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→ are sensitive to DHT

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but the follicles of the back of the head

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→ are relatively insensitive to DHT.

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So even as hair loss progresses, occipital hair is often maintained long.

That is why hair transplants also use the back of the head.

The reason is simple.

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Because occipital follicles

• are genetically less affected by hair loss
• have low DHT reactivity
• and maintain those properties even after transplantation.

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In other words, even if follicles harvested from the back of the head are transplanted to the front

those follicles keep their original characteristics and remain relatively resistant to hair loss.

But can hair loss occur at the back of the head too?

To say the conclusion first, it is possible.

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However, the cause is often different from ordinary male-pattern hair loss.

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Let me look at a few representative cases.

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1. Alopecia areata

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Alopecia areata is an autoimmune disease.

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As our body’s immune cells attack the follicles

hair suddenly falls out.

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Because this disease does not select only a specific area

• the front
• the crown
• the back of the head

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can occur anywhere.

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In severe cases it can progress to hair loss of the entire scalp.

2. Telogen effluvium

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Through stress, surgery, childbirth, rapid weight change, and so on

when the hair growth cycle is temporarily disrupted

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hair loss can occur across the whole scalp.

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When young women come to the clinic, most fall into this, but it can overlap with hereditary hair loss, so it is also a hair-loss type that requires careful testing to distinguish the cause.

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In this case

• the front
• the crown
• the back of the head

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can all be affected.

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However, most is temporary hair loss that often recovers with time (within 3–6 months).

3. Traction alopecia

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When hair is tied tightly

or continuous tension is applied in a specific direction

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the follicles are damaged and hair loss can occur.

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Representative examples

• a tightly tied ponytail
• braided hairstyles
• long-term hair extensions

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are such cases.

It often occurs among dancers, flight attendants, and athletes.

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In this case, hair loss can occur at the back of the head or the sides too.

4. Cicatricial alopecia

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Through burns, trauma, infection, and so on

when follicles are destroyed, permanent hair loss can occur in that area.

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In this case, regardless of location

• the front
• the crown
• the back of the head

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can occur anywhere.

What to check if hair loss occurs at the back of the head

If hair loss appears at the back of the head

it is important to check the following.

• The possibility of alopecia areata
• Whether there is systemic disease
• Recent major stress or surgery
• Whether medication is being taken
• Whether there is scalp inflammation

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In other words, you need to look for an uncommon cause.

This is because most hereditary hair loss almost never starts from the back of the head first.

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Therefore, if occipital hair loss appears

accurate diagnosis is important.

To sum up…

Why does the back of the head rarely go bald?

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The reasons are largely two.

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1️⃣ Occipital follicles are not sensitive to the male hormone (DHT)

2️⃣ They differ embryologically from the front.

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But in the following cases

hair loss can occur at the back of the head too.

• Autoimmune diseases such as alopecia areata
• Telogen effluvium
• Traction alopecia
• Cicatricial alopecia

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So if hair loss appears at the back of the head

rather than thinking of it as simple hair loss, accurate diagnosis is needed first.

References

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Redmond LC et al.

Male pattern hair loss: Can developmental origins explain the pattern?

Experimental Dermatology. 2023.

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Paus R, Cotsarelis G.

The biology of hair follicles.

New England Journal of Medicine. 1999.

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Messenger AG, Sinclair RD.

Follicular miniaturization in androgenetic alopecia.

Journal of Investigative Dermatology. 2006.

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Al Aboud AM, Nigam PK.

Alopecia Areata.

StatPearls Publishing. 2023.