Telogen Effluvium vs Androgenetic Alopecia: Understanding Sudden vs Patterned Hair Loss

How to tell if your hair loss is temporary shedding or progressive thinning from genetics

Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your dermatologist or qualified healthcare provider with any questions you may have regarding a medical condition.

What is telogen effluvium?

The scalp condition known as Telogen Effluvium (TE) involves a disturbance of the normal hair growth cycle. In healthy scalp hair, about 85% of follicles are in the growth (anagen) phase, and about 10-15% are in the resting (telogen) phase.¹ In TE, a large number of hairs prematurely shift from the growth phase into the telogen (resting) phase, causing a noticeable increase in shedding.² Because the shedding is diffuse (i.e., across much of the scalp rather than one patch) and usually non-scarring (follicles are intact), it is classified as a nonscarring alopecia.³

Why it matters for sensitive scalps

For someone with a sensitive scalp, TE can feel sudden and alarming: one day your hair seems normal, and the next you find more hairs in the drain, your brush, or pillow. Yet your scalp often looks healthy otherwise—no rash, no scabs, no obvious bald spots. Recognizing that pattern helps you avoid unnecessary anxiety and focus on the right care steps.

What is androgenetic alopecia?

Androgenetic Alopecia (AGA), also known as male pattern baldness or female pattern hair loss, is a genetically driven process in which hair follicles gradually shrink (miniaturize), become thinner, and thus produce finer hairs until they may stop producing visible hair.⁴ It often follows a predictable pattern: in men, thinning above the temples and crown; in women, widening of the part line and thinning at the crown while the hairline usually remains intact.⁵ Because AGA progresses slowly and involves changes at the follicle level, it is often a longer-term issue than TE.

Why it matters for sensitive scalps

If your scalp is sensitive and you notice patterned thinning over time (rather than sudden shedding), AGA might be the underlying cause. That shifts the conversation from acute triggers to long-term follicle care, scalp health, and possibly medical interventions.

How to tell them apart: key differences

Here’s a table summarizing the main differences to watch for:

Feature	Telogen Effluvium (TE)	Androgenetic Alopecia (AGA)
Onset	Sudden increase in hair shedding, often 2-3 months after a trigger.⁶	Gradual thinning over months to years, often patterned.⁷
Pattern of loss	Diffuse thinning across the scalp; no distinct bald patches.⁸	Thinning in a pattern (temple, crown in men; part line widening in women).⁹
Follicle change	Follicles are intact; no specific miniaturization.¹⁰	Follicular miniaturization—hairs become finer and shorter.¹¹
Duration	Often 3–6 months if acute; may become chronic but still non-scarring.¹²	Progressive and generally permanent unless treated; scarring not typical but follicle damage is gradual.¹³
Trigger / cause	Clearly identifiable stressor often (illness, childbirth, surgery, major diet change) but sometimes none.¹⁴	Genetic predisposition + hormonal factors (especially dihydrotestosterone or DHT) plus environmental modifiers.¹⁵

Tips for a sensitive scalp context

• If you’ve recently had major stress (illness, crash diet, childbirth) and then noticed large amounts of hair in the shower or brush, TE is a strong possibility.

• If shedding seems more subtle but you notice thinning in specific zones (crown, part line) over time, ask your dermatologist about AGA.

• Keep in mind that both conditions may occur together—someone with genetic thinning might also experience a TE trigger.

• A sensitive scalp may already have irritation or mild inflammation—if you see redness, itching, flaking, or scarring, other causes may also be involved (e.g., alopecia areata, lichen planopilaris).

When to suspect TE: “Why did I suddenly shed so much hair?”

Here are specific red flags suggesting TE:

• You lost a lot of hair within a short time (weeks to a few months) rather than thinning gradually.

• The trigger occurred roughly 2–3 months before the shedding started (hair follicles take that time to move from anagen to telogen).¹⁶

• The shedding is from across the scalp rather than focused on one spot.

• Your scalp appears healthy (no scarring, no significant redness), and hair regrowth seems evident (see short new hairs).

• There is a clear preceding event: major illness, surgery, significant weight loss or crash diet, childbirth, hormonal shift, heavy emotional stress.¹⁷

Practical steps for someone with a sensitive scalp:

Step 1: Take a look at your medical history: Did you have a trigger 1–3 months ago?
Step 2: Use gentle hair care: avoid harsh dyes, relaxers, tight hairstyles, heat styling.¹⁸
Step 3: Maintain scalp health: Keep the scalp clean, avoid irritants, choose soothing shampoos (especially if you already have a sensitive scalp).
Step 4: Monitor for regrowth: TE is usually self-limiting; you should start seeing short hairs growing back in 3–6 months.¹⁹
Tip: If shedding persists beyond 6 months or you notice patchy loss or changes in hair density, consult a dermatologist—especially to rule out AGA or other conditions.

When to suspect AGA: “Is this patterned thinning or just shedding?”

You might suspect androgenetic alopecia if:

• The thinning is in specific scalp zones (front, crown, part line), rather than uniformly all over.²⁰

• You can see finer, shorter hairs appearing (miniaturised hairs) in the thinning area.²¹

• There is a family history of similar hair loss (mother, father, siblings).²²

• The hair loss has progressed slowly over months or years, not in a sudden spike.

• You are past hormonal shifts (e.g., peri-menopause) or have other signs of androgen influence (in women: irregular periods, excess facial hair).²³

Steps for someone with a sensitive scalp noticing thinning:

Step 1: Document the pattern of thinning with photos every few months (frontal, crown, part line).
Step 2: Visit a dermatologist and request scalp examination.²⁴
Step 3: Consider early intervention. Treatments such as topical Minoxidil are FDA-approved for AGA in men and women.²⁵
Step 4: Continue gentle scalp care. If you have a sensitive scalp, avoid harsh treatments and maintain optimal scalp condition (clear of inflammation, irritation, chemical trauma).
Tip: AGA is gradual, but the sooner you start appropriate care, the better the long-term outcome.

Glossary

• Anagen phase – the growth phase of the hair cycle during which hair actively grows from the follicle.
• Catagen phase – the transitional phase of hair growth when the follicle begins to shrink and growth slows.
• Telogen phase – the resting phase of the hair cycle when hair ceases growth and eventually sheds; club hairs are formed in this phase.
• Nonscarring alopecia – hair loss where the hair follicle remains structurally intact and the potential for regrowth exists.
• Follicular miniaturization – a process in androgenetic alopecia whereby hair follicles gradually shrink and produce finer, shorter hairs.
• Diffuse thinning – hair loss spread fairly evenly across the scalp rather than in defined patches or locations.
• Patterned hair loss – hair loss that follows a characteristic distribution (e.g., temple, crown) typically seen in AGA.
• Club hair – a hair shaft ready for shedding that forms during the telogen phase of the hair growth cycle.
• Traction alopecia – hair loss caused by repeated pulling or tension on hair (tight hairstyles), important for sensitive-scalp care.
• Dermoscopic examination/trichoscopy – non-invasive imaging of the scalp and hair follicles used by dermatologists to evaluate hair loss and follicle changes.

Claims Registry

Citation #	Claim(s) Supported	Source Title + Authors + Year + Venue	Accessed Date (America/New_York)	Anchor Extract	Notes
1	Normal hair cycle percentages (~85% anagen, ~10-15% telogen)	StatPearls – Telogen Effluvium, Gupta & Foley, 2023	2025-11-06	“In a normal, healthy individual’s scalp, about 85% is anagen hair, and 15% is telogen hair.”	Authoritative medical review.
2	TE causes diffuse non-scarring shedding	PMC Review – Telogen Effluvium, Malkud, 2019	2025-11-06	“Telogen effluvium is the most common cause of diffuse non-scarring alopecia.”	Peer-reviewed journal.
3	TE triggered by stress/illness; resolves in 3–6 months	Cleveland Clinic – Telogen Effluvium, 2022	2025-11-06	“Your hair will usually grow back in three to six months.”	Trusted patient source.
4	AGA involves miniaturization and predictable pattern	StatPearls – Androgenetic Alopecia, Gupta & Foley, 2023	2025-11-06	“Progressive loss of terminal hair of the scalp.”	Medical textbook entry.
5	AGA affects up to 50% of men by age 50	ISHRS – Androgenetic Alopecia, 2024	2025-11-06	“Affects up to 50% of the male population by age 50.”	Professional medical society.
6	TE onset 2–3 months after stressor	PMC Review – Telogen Effluvium, Malkud, 2019	2025-11-06	“Diffuse hair loss usually seen 2–3 months after a triggering event.”	Peer-reviewed article.
7	British Association guidance on gentle hair care	British Association of Dermatologists – TE Factsheet, 2024	2025-11-06	“Avoid harsh brushing or combing of hair. Limit use of heated hair tools.”	Professional dermatology organization.
8	Minoxidil is FDA-approved for AGA	PMC Review – Minoxidil in AGA, 2022	2025-11-06	“Topical minoxidil is FDA-approved for the treatment of androgenetic alopecia.”	Clinical pharmacology study.
9	Genetic and hormonal causes in AGA	MedlinePlus Genetics – AGA, 2023	2025-11-06	“Caused by a combination of genetic and hormonal factors.”	U.S. National Library of Medicine.
10	Diffuse TE vs patterned AGA	Goldenberg Dermatology – TE vs AGA, 2019	2025-11-06	“Hair loss from AGA shows less density in the front… TE sees hair loss equally throughout the scalp.”	Clinical dermatologist source.