What Causes Hair Loss? A Dermatologist’s Complete Guide
Medically reviewed by Dr. Hessa Bin Haider, Board-Certified Dermatologist & Aesthetic Physician, DHA Licensed 20+ years’ experience, 15,000+ patients treated, 4.9/5 across 312 Google reviews.
Hair loss feels like one problem, but it’s actually the visible symptom of several very different underlying causes, from genetics to hormones to something as temporary as a stressful few months. Understanding what causes hair loss in your specific case is the first step toward the right treatment, since a genetic pattern and a stress-triggered shedding phase require completely different approaches, even though they can look similar at first glance. This guide breaks down every major category, from the most common causes to the ones patients often overlook, with hair loss causes explained clearly enough to help you recognize which one applies to you before your first consultation.
The Most Common Cause: Genetics (Androgenetic Alopecia)
Genetics is by far the leading cause of hair loss, and understanding how it actually works helps explain why some people start thinning in their twenties while others keep a full head of hair well into their sixties.
How Male and Female Pattern Hair Loss Works
Androgenetic alopecia, commonly known as male or female pattern hair loss, is driven by a hormone called dihydrotestosterone (DHT), a byproduct of testosterone. In people who are genetically sensitive to DHT, this hormone gradually shrinks, or miniaturizes, hair follicles over time. Each growth cycle produces a slightly thinner, shorter strand than the last, until some follicles stop producing visible hair altogether. In men, this typically shows up as a receding hairline and thinning at the crown. In women, it usually appears as a widening part and diffuse thinning across the scalp, rather than a receding hairline, since the underlying pattern differs by sex even though the mechanism is the same.
Why It’s Hereditary, and Why It Isn’t Always From Your Father’s Side
Androgenetic alopecia runs in families, but the old idea that it only comes from your mother’s father is a myth. The genes involved come from both sides of the family, which is why looking at hair loss patterns across your whole family tree, not just one parent, gives a more accurate picture of your own risk. Having a strong family history doesn’t guarantee you’ll experience the same degree of hair loss, but it does mean your follicles are more likely to be sensitive to DHT over time.
Tip:
Hair loss that follows a clear pattern, a receding hairline, thinning at the crown, or a gradually widening part, is more likely to be genetic than a temporary shedding phase, which tends to be more diffuse and sudden
Genetics is the dominant cause of hair loss by a significant margin: androgenetic alopecia affects up to 80% of men and 50% of women at some point in their lives, and accounts for roughly 95% of all hair loss cases overall.
Hormonal & Medical Causes of Hair Loss
Beyond genetics, a range of hormonal and medical conditions can trigger hair loss on their own, and identifying them matters because many of these causes are treatable once the underlying condition is addressed.
Thyroid Conditions and Hormonal Imbalance
Both an underactive thyroid (hypothyroidism) and an overactive one (hyperthyroidism) can disrupt the hair growth cycle, pushing more follicles than usual into a resting phase and causing diffuse shedding. This type of hair loss often improves once thyroid levels are brought back into a normal range, which is why thyroid function is one of the first things checked in a proper diagnostic workup.
Postpartum and Pregnancy-Related Shedding
Pregnancy hormones temporarily extend the hair’s growth phase, which is why many women notice thicker hair during pregnancy. After delivery, hormone levels drop rapidly, and all those hairs that were “held” in the growth phase shift into shedding at once, typically two to four months postpartum. This is usually temporary and resolves on its own within six to twelve months, though it can feel alarming while it’s happening.
PCOS and Other Androgen-Related Conditions in Women
Polycystic ovary syndrome (PCOS) and other conditions that raise androgen levels in women can trigger a pattern of hair thinning similar to androgenetic alopecia, since the underlying hormonal mechanism overlaps. Women with PCOS-related hair loss often notice it alongside other symptoms, such as irregular cycles or increased facial or body hair, which is a useful clue for a dermatologist working to identify the root cause.
In Dubai’s largely expat population, our clinic sees a notably high volume of postpartum shedding and relocation-related stress shedding cases. Routine bloodwork during these consultations frequently uncovers thyroid or vitamin deficiencies that went undiagnosed before the patient moved, or that developed during the adjustment period, which is one reason a full diagnostic workup matters even when the hair loss seems to have an obvious trigger.
Stress, Diet & Lifestyle Factors
Beyond genetics and hormones, everyday stress, nutrition, and even hairstyling habits play a real role in hair loss, and this is where hair loss causes explained most often surprises patients, since these factors are usually reversible once addressed.
Telogen Effluvium: Stress-Triggered Shedding Explained
Telogen effluvium is a temporary form of diffuse shedding triggered by a significant physical or emotional stressor, such as surgery, illness, a major life event, or even a crash diet. The stressor pushes a larger-than-normal number of hair follicles into the resting (telogen) phase all at once. Because hair sheds roughly two to three months after entering this resting phase, the shedding often appears well after the stressful event has passed, which is part of why patients are frequently confused about what triggered it.
Iron, Vitamin D, and Protein Deficiencies
Hair follicles are metabolically demanding, and low levels of key nutrients, particularly iron (ferritin), vitamin D, and protein, can push more hairs into shedding than usual. Iron deficiency is one of the most common nutritional causes of hair loss in women specifically, even in the absence of anemia. Correcting a genuine deficiency, confirmed through bloodwork rather than assumed, often leads to a noticeable improvement in shedding within a few months.
Hairstyling Habits: Traction Alopecia From Tight Styles and Heat Damage
Traction alopecia develops from repeated tension on the hair, from tight ponytails, braids, weaves, or extensions, which gradually damages the follicle at the root. Unlike other causes on this list, it’s largely preventable, since the hair loss is directly tied to styling choices rather than an internal cause. Heat damage from frequent styling tools can further weaken the hair shaft, making it more prone to breakage that can look like thinning even when the follicles themselves are healthy.
Tip:
Shedding that started 2 to 3 months after a stressful event, illness, or crash diet is a classic sign of telogen effluvium, not permanent hair loss, and it typically resolves on its own once the underlying trigger has passed.
Hair Loss Causes Explained: Less Common but Important Conditions
Beyond the categories covered so far, a handful of less common but clinically important conditions round out the full picture of hair loss causes explained, and recognizing them matters because several require a different treatment approach entirely.
Alopecia Areata (Autoimmune Patchy Hair Loss)
Alopecia areata is an autoimmune condition in which the immune system mistakenly attacks hair follicles, causing sudden, well-defined patches of hair loss, most often on the scalp but sometimes elsewhere on the body. Unlike androgenetic alopecia, it doesn’t follow a predictable pattern and can appear at any age. It affects roughly 2 in every 1,000 people, and while the exact trigger varies, it’s considered distinct from both genetic and stress-related hair loss and typically requires a different treatment pathway.
Scalp Conditions: Dandruff, Seborrheic Dermatitis & Fungal Infections
An unhealthy scalp environment can contribute to hair loss even when the follicles themselves aren’t directly damaged. Conditions like seborrheic dermatitis cause inflammation and flaking that can interfere with normal hair growth, while fungal infections such as tinea capitis directly damage the hair shaft and follicle. Persistent itching, flaking, redness, or scaling on the scalp is worth having assessed, since treating the underlying scalp condition often resolves the associated shedding.
Medication-Induced Hair Loss
A number of common medications, including certain blood thinners, blood pressure medications, antidepressants, and chemotherapy drugs, can cause hair loss as a side effect. This typically presents as diffuse thinning that develops within weeks to a few months of starting the medication, and it’s usually reversible once the medication is adjusted or stopped, ideally in coordination with the prescribing doctor rather than independently.
Dr. Hessa’s take:
One of the most important things I tell patients is that ‘hair loss’ isn’t a single diagnosis, it’s a symptom with a long list of possible causes behind it. Two patients can describe the exact same thing, thinning hair, and be dealing with completely different conditions underneath. My first job is always narrowing down which category it actually falls into, because the treatment for a genetic pattern, a nutrient deficiency, and an autoimmune condition are not the same, and treating the wrong one wastes time patients don’t need to lose
How Hair Loss Is Diagnosed
A proper diagnosis is what separates effective hair loss treatment from guesswork, and it typically involves three components working together to identify the actual cause before any treatment plan is built.
Trichoscopy and Scalp Examination
Trichoscopy uses a specialized magnified camera to examine the scalp and hair follicles in detail, revealing patterns invisible to the naked eye, such as follicle miniaturization, inflammation, or scarring. This visual assessment helps distinguish between genetic thinning, autoimmune patchy loss, and scalp-related causes, often narrowing down the likely diagnosis before any lab results come back.
Blood Tests (Ferritin, Thyroid Panel, Vitamin D, Hormones)
Bloodwork is essential for ruling in or out the hormonal and nutritional causes covered earlier. A standard hair loss panel typically checks serum ferritin, a full thyroid panel, vitamin D, and relevant hormone levels, since several of these causes present with identical symptoms but require entirely different treatments. Serum ferritin in particular is a highly reliable marker: levels at or below 15 μg/L confirm iron deficiency with around 98% specificity in premenopausal women, making it one of the most clinically useful single tests in a hair loss workup.
The Hair Pull Test and Shedding Pattern Assessment
A simple hair pull test, gently tugging a small section of hair to see how many strands come away, helps gauge how active the shedding is at the time of the visit. Combined with a detailed history of when the shedding started, how it’s distributed, and whether it follows a pattern, this assessment helps place the case into one of the categories covered above, genetic, stress-related, autoimmune, or medical.
Clinical guidance consistently supports this blood-panel-first approach: dermatology literature specifically recommends evaluating serum ferritin and vitamin D levels before starting treatment in patients with diffuse hair loss, since treating empirically without this data risks missing a correctable underlying cause and delaying an effective treatment plan.
In Dubai, this full diagnostic workup is available locally through a DHA-licensed consultation, which removes the guesswork of interpreting an at-home test kit or relying on an unregulated online consultation that can’t order or properly interpret bloodwork.
When to See a Hair Loss Dermatologist
Not every hair loss concern requires an immediate appointment, but certain signs point clearly toward needing a professional evaluation rather than waiting it out.
Red Flags That Warrant a Professional Evaluation
Patchy hair loss, especially well-defined bald spots, is worth having assessed promptly, since it often points to alopecia areata or a scalp condition rather than typical pattern thinning. Sudden, dramatic shedding, noticeably more hair than usual on your pillow, in the shower drain, or on your brush, also warrants attention, as does any scalp pain, tenderness, redness, or visible scarring, which can indicate an underlying inflammatory or infectious process. These signs don’t necessarily mean something serious, but they’re not things a hair loss dermatologist in Dubai would recommend waiting on.
Why Early Diagnosis Improves Treatment Outcomes, Especially for Genetic Hair Loss
For genetic hair loss specifically, timing matters more than most patients realize. Treatments like minoxidil and PRP work by supporting follicles that are still active, but once a follicle has been fully miniaturized and stops producing hair altogether, no treatment can bring it back. This means the earlier genetic thinning is identified and addressed, the more follicles there are still available to respond to treatment, and the better the long-term outcome tends to be.
Tip:
Waiting to “see if it gets better” is the most common reason patients arrive with more advanced, harder-to-reverse hair loss. What feels like a small, manageable change often has months or years of head start by the time it’s addressed.
Why Choose Dr. Hessa Bin Haider as Your Hair Loss Dermatologist in Dubai
Choosing the right dermatologist for hair loss matters because, as covered throughout this guide, an accurate diagnosis is the foundation of every effective treatment plan, and that starts with a physician who investigates thoroughly rather than treating symptoms generically.
Dr. Hessa Bin Haider is a Board-Certified Dermatologist & Aesthetic Physician, DHA licensed, with over 20 years of clinical experience in Dubai. She has treated more than 15,000 patients, with a 98% satisfaction rate and a 4.9/5 rating across 312 Google reviews.
What sets her approach apart is a full diagnostic workup before any treatment begins, combining trichoscopy, bloodwork, and a detailed history to identify the actual cause rather than assuming one. Her treatment options span from PRP to Exosome hair therapy, allowing her to match the treatment to the diagnosis rather than offering a single one-size-fits-all solution. Her clinic is based in Barsha Heights, Dubai.
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FAQs
What causes hair loss in women specifically?
Women’s hair loss often stems from hormonal shifts, pregnancy, menopause, PCOS, or thyroid conditions, alongside genetic androgenetic alopecia, which presents as diffuse thinning rather than a receding hairline. Iron deficiency is also a notably common contributing factor in women. Because multiple causes can overlap, bloodwork is usually needed to identify the specific driver.
Can stress alone cause hair loss?
Yes, through a condition called telogen effluvium, where a significant stressor pushes an unusually large number of follicles into a resting phase at once. Shedding typically appears two to three months after the stressful event, which is why the connection isn’t always obvious. This type of hair loss is usually temporary and resolves once the trigger has passed.
Is hair loss reversible?
It depends on the cause. Stress-related, nutritional, and medication-induced hair loss are often fully reversible once the underlying trigger is addressed. Genetic hair loss can be slowed or partially reversed with early treatment, but fully miniaturized follicles that have stopped producing hair generally can’t be restarted, which is why timing matters.
What vitamin deficiencies cause hair loss?
Low iron (ferritin) and vitamin D are the two most well-documented nutritional deficiencies linked to hair loss, particularly in women. Protein deficiency can also contribute, since hair is primarily made of protein. A blood test is the only reliable way to confirm a deficiency rather than assuming one based on diet alone.
When should I see a hair loss dermatologist in Dubai?
See a dermatologist promptly for patchy hair loss, sudden or dramatic shedding, or any scalp pain, redness, or scarring. For gradual thinning, earlier evaluation still improves outcomes, since genetic hair loss responds best to treatment before follicles are fully miniaturized and stop producing hair.
How is the cause of hair loss diagnosed?
Diagnosis typically combines trichoscopy to examine the scalp and follicles, blood tests covering ferritin, thyroid function, and vitamin D, and a hair pull test to assess active shedding. Together, these narrow down which of the underlying causes, genetic, hormonal, nutritional, or autoimmune, is actually responsible.
Resources:
https://www.ncbi.nlm.nih.gov/books/NBK278957/
https://www.ncbi.nlm.nih.gov/books/NBK430924/