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Why is my hair falling out? – 23 Causes of Hair Loss, by a Dermatologist

man detecting bald spots on scalp and trying to understand causes of hair loss

We all love our hair.

It’s the very thing that completes our appearance.

Whatever your go-to hairstyle is, if your hair looks good, you feel good; there’s no arguing that.

Good Hair Day Vibes!

Seeing a few strands of hair fall out when you’re combing it probably shakes your mood. But once we see a real sign of hair loss like our hairline receding or our hair thinning, that’s the real mood killer.

The first step to stopping and/or reversing hair loss is, just as it is with any other medical condition, is to understand the reason behind it.

So in this article, I will explain every known reason behind hair loss and help you identify the cause of your hair thinning.

Let’s start with the science behind a hair falling out:

Science Behind Hair Loss, Simplified

Hair is made of keratin, a structural protein that is also found in your skin and nails too.

Produced in the hair follicles right at the outside layers of your skin, a hair strand is a product of hair follicles’ lifecycle.

What a hair really looks like under your skin, from Wikipedia

A hair follicle is produced, then it grows for a while, then it slowly dies and new hair replaces it.

So around 50-100 hair follicles in your scalp die every day and are replaced with new ones. That much loss is unnoticeable since the average person has 100,000 hairs on the head.

When a hair follicle on your head dies, it falls out, which is what you see when you comb through your hair. Your hair falling out is the most natural thing in the world, and as long as the new hair grows to replace the lost ones, you’re OK.

You only go bald if one of these two situations are present:

1⃣ You’re losing more hair than you can reproduce

2⃣ You’re reproducing less hair than you lose

I know these two sound like the same thing, but they’re not.

You can either be losing hair fast or producing new hair slowly, which both result in a number of hair follicles permanently reduced.

And all the reasons behind hair loss cause either of these two situations. Identifying what it is is up to you or your dermatologist.

Now let’s see all the reasons that might be causing the gap between dead and born hair follicles:

23 Causes for Hair Loss

Here are 25 of the most common reasons behind hair loss and baldness:

1- Genetic Background

You are way more likely to experience hair loss if you have a family history of hair loss, either on the maternal or paternal side.

The most widespread cause of hair loss is genetic male and female pattern hair loss. There’s a common idea that suggests if your paternal grandfather is bald, you’re going bald. If not, you’re safe.

Although this can be considered a variable in hereditary hair loss, there’s more to a genetic background in terms of hair loss, much more. Researchers have found over many years and across different studies that over 280 genes play a role in hair loss, but you don’t need to take a look at each one to know if genetics is what causes the hair loss for you.

To keep it simple, the history of hair loss among relatives from maternal and paternal sides should be asked to know if your hair loss comes from a genetic background. If there’s a pattern in the family history, hair loss can be connected to your genetics.

“If you look at identical twins — who share 100 percent of their genes — typically, they have a very similar pattern of hair loss.”

Markus Nöthen, a geneticist at the University of Bonn
Hereditary Hair Loss in Twins, from a study by Dow Stough

2- Age

Overall cell production, and production of any kind, slow down with age.

And hair growth is not an exception.

Especially after your 40s, you’re likely to experience a receding hairline and overall thinning in your hair. This might not come in a pattern, but if you have a genetic background for balding it is likely to worsen.

3- Androgen Sensitivity

This one requires a bit of explanation, so bear with me:

Androgens are a group of hormones that are present in both men and women, and play a role in male traits and reproductive activity, such as testosterone and dihydrotestosterone (DHT).

Around puberty, androgens stimulate axillary and pubic hair in both sexes. However, later, high amounts of androgens cause hair loss.

In simplest terms, high levels of androgens, especially DHT, cause your androgen-sensitive hair follicles to shrink and shorten the hair growth cycle. This ends up with you having thinner new hair that falls out faster.

Testosterone, DHT, Androgen Sensitivity and Hair Growth Cycle Mechanisms

In addition to the number of androgens, the sensitivity of your hair follicles to androgens, which is determined by your genetics, plays a huge role in hair loss.

Generally, hair follicles on the side and back of the head are inherently more DHT resistant since they have fewer ARs (Androgen Receptors). When they are transplanted to a recipient area, they keep their DHT resistance which makes the hair transplant surgery results permanent.

While it is proven by research that male pattern baldness (AGA) is experienced mostly when there’s a high level of DHT and Androgen Sensitivity together, only one-third of women with AGA show abnormally high androgen levels.

4- Metabolic syndrome and insulin resistance

Metabolic syndrome (MetS) refers to a group of metabolic abnormalities that include hypertension, central obesity, and atherogenic dyslipidemia.

It is strongly associated with the risk of developing diabetes and heart diseases. Insulin resistance, on the other hand, refers to high plasma insulin levels in the blood and can also be considered an abnormality in MetS.

Those who have metabolic syndrome and insulin resistance are more likely to experience hair loss than those who don’t since the three conditions are tied together as studies suggest.

According to the NCEP ATP III definition, metabolic syndrome is present if three or more of the following five criteria are met:

Metabolic Stress on Body (Source)

A waist larger than 101cm (40 inches) for men or 89cm (35 inches) for women

Fasting blood sugar over 100 mg/dl

Fasting triglycerides over 150 mg/dl

Blood pressure over 130/85 mmHg

Fasting HDL cholesterol less than 40 mg/dl for men or 50 mg/dl for women

5- Medications

Medications are known to interfere with the normal hair growth cycle, causing permanent or temporary hair loss.

The most common medications that cause hair loss, or alopecia, are anticoagulants (‘blood thinners’ such as warfarin), chemotherapy agents used in cancer treatment, and immunosuppressant drugs taken by organ transplant recipients.

Other medications that can cause a form of hair loss include:

  • Antidepressants
  • Antithyroid Agents
  • Anabolic Steroids
  • Antibiotics and Antifungal Drugs
  • Birth Control Pills
  • Epilepsy Drugs
  • Mood Stabilizers
  • Weight Loss Drugs
  • Vitamin A rich drugs such as Acne Medications

The mechanism of action for each medication is slightly different, but all work by inhibiting different stages of the hair growth cycle. Medication-induced alopecia is usually reversible once the medication has stopped being taken, but may take up to 12 months for the hair to regrow.

6- Oxidative Stress

Oxidative stress is referred to as the imbalance between the production of free radicals and antioxidants in your body.

Your body can’t produce enough antioxidants to match free radicals, and the surpass of free radicals damage your cells and DNA.

Oxidative stress can be caused by:

Excessive exposure to sunlight


Exposure to chemicals

Radiation therapy to head


Alcohol consumption

Diets high in fat and processed sugar

Certain medications

Oxidative stress will simply harm your cells and your DNA, accelerating aging and in the scalp, damaging hair follicles that produce hair. It was recently found by a study that oxidative stress plays a huge role in premature hair loss and baldness.

Oxidative Stress Caused Free Radicals, Cell/DNA Damage, and Antioxidant Neutralization Mechanisms

7- Scalp Conditions – oily scalp

Sebum is an oily, waxy substance secreted by our body. It coats, moisturizes, and protects your skin, and protects/supports your healthy hair. It is a natural part of our scalp and thus everyone’s hair gets oily sometimes.

While being careful about hair hygiene, we shouldn’t forget that little to normal amounts of sebum/oil are good for the scalp health. Some of the shampoos are pretty strong and might clean up all the healthy sebum.

An oily scalp, often caused by genetics, refers to a condition where an excess amount of oil (sebum) is released in your scalp.

And excess amounts of oils can and will trap and attract dirt, dandruff, and product build-up, which clogs pores and prevents new hair growth.

8- Thyroid Conditions

Thyroid diseases such as hyperthyroidism and hypothyroidism can and will cause diffuse hair loss and many other adverse effects on your body if they’re not treated.

The hair thinning and loss is diffuse (no patching or bald spots) is all over the scalp.

Thyroid conditions can disrupt hormone production processes, especially the T3 and T4 thyroid hormones which help produce hair at the root.

So, a thyroid disease might mean that you’re not getting back the hair you’ve lost.

9- Iron Deficiency Anemia

What is Iron Deficiency Anemia?

It is a condition in which the blood doesn’t have enough healthy red blood cells. These cells are responsible for carrying oxygen to organs and tissues.

What are Iron Deficiency Anemia Symptoms?

  • Extreme weakness
  • Pale or yellowish skin
  • Fatigue
  • Irregular heartbeats
  • Headache
  • Cold hands and feet
  • Brittle nails
  • Poor Appetite
  • Shortness of breath
  • Chest pain
Iron Deficiency Anemia Definition and Symptoms

How does Iron Deficiency Anemia affect hair follicles?

This topic is somewhat controversial.

Some researchers found out it is causing hair loss, others say there is no clear and proven relation between them.

A study published in the Journal of Korean Medical Science found that Iron Deficiency is a clear factor of developing or worsening Female Pattern Hair Loss, especially in premenopausal female patients.

However, in the same study, it is clearly indicated that:

“Iron Deficiency’s role in Male Pattern Hair Loss is hard to conclude.”

Bodies of patients who experience a severe iron deficiency may start cutting oxygen to organs and tissues that are not vital.

Could you guess what needs oxygen? Yes, your hair. So, iron deficiency might cause hair loss by stopping the body from providing your scalp with oxygen.

10- Lichen Pilanopilaris

Lichen Planopilaris is an inflammatory condition that causes scarring hair loss. It destroys the hair follicle and then replaces it with scarring, resulting in permanent hair loss (The hair follicles do not regrow).

The cause of this disease is unknown. It is known that the body’s immune system is involved in the process but the trigger is mysterious.

What are the symptoms of Lichen Pilanopilaris?

If you feel itchiness, tenderness, pain, and burning in your scalp and start to realize areas of hair loss you might be experiencing the disease.

It can also be seen in your mouth, skin, genitals, nails.

White dots without hair follicles on your scalp can be detected by a dermatologist in a trichoscopic examination.

Lichen Planopilaris (Source)

11- Tractional Alopecia

Traction alopecia is hair loss that stems from mechanical damage to hair follicles.

  • Repeatedly pulling on your hair,
  • traumatic hairstyling,
  • chemical appliance via styling care or hair coloring products
  • heat appliance via blow dryer or hair straighteners
  • and often wearing the hair in ponytail, bun or braids might cause tractional alopecia.
Traction Alopecia Type Hair Loss in Women, Source

12- Low Blood Circulation

If you’re not someone that regularly exercises, you’re likely to experience a decrease in your blood circulation.

This will eventually translate to a decreased blood flow to your scalp, leaving your hair without oxygen and nutrition which can cause hair loss or accelerate your existing condition.

In addition, people who are overly stressed can experience a decrease in blood flow as well.

In this case, the stress hormone cortisol takes over and puts your body into a “flight or fight mode” which diverts blood away from non-essential parts such as the hair follicles for immediate survival.

13- Anxiety and Stress

Although anxiety is not directly related to hair loss, stress caused by anxiety and other influences can cause mainly two different types of hair loss:

Alopecia areata:

In this type of hair loss, hair on the head falls out in patches.

Commonly caused by stress, alopecia areata is a condition where the immune system attacks scalp hairs, eventually causing the loss of hair.

Only in the United States, about 6.8 million people are affected by the disease.

The patchy hair loss may be sudden or gradual. There might be itching or burning in the affected area before hairs start to fall.

The condition may result in total balding in case it is not treated by a dermatologist.

Alopecia Areata is a stress-related patchy hair loss

Telogen effluvium:

In this condition, the hair follicles that produce hair are pushed to a resting phase from their neutral phase; which can eventually result in them falling out of your body.

In a normal person, 85% of the hairs are actively growing in the anagen phase and 15% are in the resting phase.

If there is a traumatic event or stress, the majority of hair follicles in the anagen phase might change phase into the resting phase. Eventually, these hair follicles are pushed out by the new hair coming in 2 months after the shock causing sudden hair loss. Actually, it is a temporary hair loss, and falling out is a sign of hair regrowth.

Lost Hair Due to Telogen Effluvium on the Comb

14- Lack of Sleep

Sleep connects the time a person spends awake with bodily functions such as hair growth and cell division.

In short, we can say that less sleep means less hair follicle growth.

But let’s go a bit more into detail:

In “Sleep Loss Alters Waking Activity in Human Epidermal Keratinocytes,” published in the January 2014 issue of Journal of Investigative Dermatology, researchers studied how cells behave when deprived of restorative rest.

They discovered that with too little sleep, skin cells numbered fewer and formed inappropriately small connections with one another; both conditions are hallmarks of alopecia areata, the autoimmune disease that causes hair loss.

Sleeping too little also negatively affected the number of melanocytes in the mice studied, which produce pigment for coloring skin and hair.

Although the real effects of lack of sleep on hair loss were recently made clear, you could say the physicians guessed the relation ages ago:

In his book “The Organon of Medicine,” published in six volumes between 1810 and 1820, German physician Samuel Hahnemann reported on dozens of case studies involving patients with varying degrees of alopecia who were treated with homeopathic remedies made from various species of tree moss. Today, many dermatologists recommend that patients receive acupuncture treatment for hair loss, but in centuries past doctors often prescribed hair loss patients with no alternatives for alopecia to sleep on moss-stuffed pillows; which improved sleeping quality back then.

15- Nutrition Deficiencies

Lack of certain nutrition will affect different parts of your body and the physical and chemical processes inside. Especially mineral and vitamin deficiencies correlate with alopecia.

As I’ve mentioned before, Iron Deficiency can be a factor that causes your hair loss, but here are a few other nutritions you should really look out for, the most important of them being:

  • B12 and Folic acid deficiencies lead to megaloblastic anaemia , that is basically having too many immature red blood cells causing excessive hair loss, balding, dandruff and dryness.
  • Zinc is important for the production of insulin which is necessary for the uptake of glucose by muscle cells so they can produce energy. With a zinc deficiency you have an increased risk of having dry skin and dandruff. This causes the skin to be more irritated so it’s susceptible to scalp infections like ringworm.
  • Vitamin A is crucial for cellular growth of hair follicles. However, consumption of too much vitamin A may lead to vitamin A toxicity according to the research. Thus, under and over supplementing can cause hair loss.
  • Vitamin E is helps body to protect itself against free radical damage. As we mentioned above, free radicals damage hair cells.

Other than that, nutritional deficiency of

  • Niacin,
  • Fatty Acids,
  • Selenium,
  • Vitamin D,
  • Biotin,
  • Amino acids and Proteins are also known to cause hair loss

The patient should see a dermatologist (if there is no dermatologist, a family physician or general practitioner may be preferred as the last resort.) for a blood test to detect an exact nutritional deficiency causing visible hair loss.

16- Extreme Dietary Habits

As with every health issue, your diet can be a strong variable in hair loss.

Overall, balanced and healthy diets will promote hair growth by providing your body with the resources it needs. But if your diet is on the extreme side of the spectrum, you might need to reconsider a few things.

For example, you should definitely steer away from overeating:

1. Egg yolks:

Egg yolks have a high content of sulfur, which is a strong stimulus for the sebaceous glands.

When you overconsume egg yolks, you’ll start producing excess sebum.

And if the amount of sebum increases around your scalp, you’ll end up having an oily scalp that will cause, as we’ve mentioned before, less hair growth.

2. Sugar:

Studies have shown that people suffering from hair loss ate foods with high sugar content more frequently, especially the ones with processed sugars.

This may be due to the fact that glucose increases glycoside levels, which can cause toxic effects on cells and interfere with their normal division. Also, it has been discovered that too much insulin stimulates the process of hair loss, therefore avoiding consuming too many sugary foods is likely to improve your condition.

3. Pepper:

I hate to be that guy but, you will also need to control your black pepper intake.

Pepper in certain concentrations can cause severe itching and irritation of the skin, which in turn accelerates hair loss and balding. This is due to the chemical substance piperine inside of the pepper, which again, stimulates sebum secretion and gives you an oily scalp.

4. Vitamin A

As a fat-soluble vitamin, the excess amounts of Vitamin A are not directly thrown out of your body.

So consuming high amounts of Vitamin A causes hypervitaminosis A, which eventually leads to skin irritation, coarse hair, and partial hair loss.

5. Foods with High Glycemic Index

Again, foods with a high glycemic index will cause your insulin levels to increase, therefore making you more likely to experience hair loss.

17- Rapid Weight Loss

Your body doesn’t like it when you suddenly change its balance.

When you lose a ton of weight out of nowhere, every part of your body will need to adjust how they work, the number of chemicals and hormones and enzymes they produce, and so on.

So any sudden change in your body mass index will bring up high levels of stress in your body, which will then cause telogen effluvium, where the growth of new hair by your hair follicles will be significantly decreased.

18- Protein Powder Intake

Some of the protein powders that contain whey isolates are known to contain anabolic steroids, which makes you produce higher levels of dihydrotestosterone (DHT) and may eventually lead to hair loss.

19- Smoking

Smoking can cause or accelerate hair loss in many ways.

The most obvious way is by affecting your blood circulation. Toxic chemicals a cigarette consists of will have a high toll on your blood circulation and reduce the amount of blood that flows into your scalp, leaving hair follicles with less nutrition and oxygen and ending up in them falling out.

And another way it can harm your hair and prevent hair growth is through the pollution it will produce around you. The smoke cigarettes produce stays in the environment you smoked in for a long time, and consists of toxic substances. When your hair and scalp are exposed to this pollution, they will be adversely affected by them.

20- Alcohol Consumption

Excessive amounts of alcohol consumption can lead to serious dehydration, not just only to your hair and scalp, but throughout your whole body.

This dehydration has a toll on your hair follicles and hair strands and can slow down hair growth while making your hair fall out.

21- Polycystic Ovary Syndrome (PCOS)

PCOS is a hormone disorder related to women’s ovaries and has three main symptoms, one of which is high levels of androgen.

As we’ve mentioned before, high levels of androgen aside from teenage years are never a good sign for your hair.

In most cases, excess androgen will cause noticeable hair loss that will show itself with an overall thinning.

22- Syphilis

Syphilis is an STI (sexually transmitted infection) that is divided into four stages based on its progression and symptoms.

If untreated, starting from the secondary stage, Syphilis can cause bald patches in your scalp where it affects. However, these bald spots are usually not permanent and recover when treated.

23- Poisoning

Obviously, most chemicals are extremely harmful to our bodies.

Especially for people that work in labs or chemical substance production lines, exposure to poisonous substances such as mercury, lithium, thallium, and arsenic can result in hair loss.

Can You Prevent or Revert Hair Loss?

Stopping hair loss

Once you’ve eliminated all the reasons for your hair loss, the amount of hair that’s falling out of your scalp should get back to normal.

You can also try one of the various ways of minimizing hair loss, which you can find out more about in our extensive guide:

Read: 15 Working Methods to Prevent Hair Loss

If your hair loss is completely based on genetic factors and other causes are not present, you won’t be able to stop hair loss to a certain level. However, once your androgenic alopecia has settled, there are ways to get back to your natural hairline:

Reverting hair loss

If your hair loss has advanced to a significant and visible level, you might be looking to regrow your lost hair.

There are numerous non-medical/medical hair loss treatments such as pharmacological medications like Rogaine (Minoxidil) and Finasteride (Propecia), hair massage, herbal therapies, PRP, exercise, and laser therapy that are said to stimulate hair growth in balding areas, some of which are backed up by studies.

Also, there are surgical methods such as hair transplantation which is a sure way to get back to your natural look. All of these methods can be found in our comprehensive guide:

Next Steps

Yes, we know that detecting the root cause of hair loss is not easy especially if the underlying medical conditions are unclear.

Each case is unique and there are a lot of treatments for hair loss (some of them are useless and just marketing). Therefore, only seeing thousands of cases might bring enough experience to diagnose and treat hair loss.

If you need a further diagnosis, assistance, and clinical examination for understanding your hair loss, minimizing it, or getting your natural hairline back, you can always contact me or other hair loss expert dermatologists of UnitedCare:

Understand the Reasons Behind Your Hair Loss

Preserve or regrow your hair with a Dermatologist

Frequently Asked Questions (FAQs)

What is the cause of hair loss in females?

For women, the most common causes of hair loss are as follows:

  • Tractional Alopecia (pulling hair too much)
  • Anxiety and chronic stress
  • Certain medications such as chemotherapy drugs and Vitamin A rich meds
  • Age
  • Androgen sensitivity
  • Extreme dietary habits and rapid weight loss
  • Smoking and alcohol consumption

How can I stop my hair loss?

Eliminating the variables that cause your hair loss is the first step to stopping your hair loss. Be aware that there is not a magical solution. You may start with lifestyle changes and dietary updates. You can reduce alcohol consumption and smoking, and start taking supplementary and pharmacological (finasteride, minoxidil) medications. Most importantly, consult with a dermatologist whose specialty is scalp and hair loss to understand the root cause.

Why am I suddenly losing so much hair?

Sudden loss of hair can be caused by multiple reasons, most common of which are:

  • Stress, trauma
  • Extreme changes in diet
  • Protein powder intake
  • Certain medications
  • Poisoning from chemical substances
  • Male pattern baldness (Androgenetic Alopecia)

What food causes hair loss?

Especially foods that are high in processed sugars are proven by the study to cause hair loss. Other than that, foods that cause insulin increase such as bread, flour, and sugar with alcohol endanger hair growth as well.

What are the types of hair loss?

  • Androgenetic Alopecia: It is a medical term of hereditary male or female pattern baldness.
  • Telogen Effluvium: It is a type of noticeable hair loss after an emotional shock and stress happening when many hair follicles go into telogen phase (a.k.a resting phase).
  • Anagen Effluvium: It occurs after chemotherapy or radiation therapy exposure during the anagen or growth phase of hair follicles.
  • Alopecia Areata: It is an autoimmune condition in which the immune system attacks hair follicles after a stressful event.
  • Scarring Alopecias (Cicatricial Alopecia): It is a skin disease in which Inflammation on the skin causes permanent loss of hair. Before a hair replacement surgery, this condition should be fixed. Otherwise the operation will definetely fail.
  • Alopecia Universalis: In this type of hair loss, all hair son the body (pubic, chest, leg, and scalp) fall out. Hair follicles do not die and can regrow.
  • Tinea capitis: It is a ringworm caused fungal infection resulting in a patchy bald spots on the head. Brittle and broken hairs, itchy,red and ring-like bald spots are some of the symptoms of Tinea Capitis.

Utkan Kızıltaç, MD

Chief Physician and Dermatologist Hair Transplant Surgeon of UnitedCare, a dermatology clinic helping patients become the best version of themselves.

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