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Hair loss causes

Hair loss, hair thinning, and balding are all extremely common. More than 80% of men and half of women will experience some form of hair loss in their lives.

Hair loss causes differ from person to person. They could be genetic, stress-related, or a side effect from medication.

Keep reading to find out the main causes of hair loss and which ones might be affecting you.

Medically reviewed by Dr. Caroline Fontana Written by our editorial team Last reviewed 06-01-2024

Hair loss myths

Over time, various myths surrounding hair loss causes have become well known, despite not being based on scientific fact. The following actions might cause some damage to your hair, but do not cause permanent hair loss.

Hat icon Wearing hats

Wearing a tight-fitting hat has been believed to lead to balding and hair loss, but no scientific evidence is able to prove this.

Swimming icon Swimming in chlorinated water

Whilst the chlorine used to disinfect swimming pools can damage and dry out your hair, it does not cause hair loss or balding.

Hair dryer icon Using hair dryers

Some people assume that the heat from hair dryers can cause hair loss. This is untrue. The heat from hair dryers can only cause hair damage by drying out your scalp.

Sun cream icon Applying suncream to the scalp

Some ingredients in sunscreen have been thought to cause hair loss. This is not the case, and SPF should be applied to the scalp to prevent sun damage.

Genetic causes of hair loss

Hereditary hair loss

The most common hair loss cause in men is pattern baldness, also known as androgenic alopecia. This is a genetic condition that affects more than 50% of men by the time they reach 50 years old.

Male pattern baldness can start as early as in your twenties, with the first sign being a receding hairline. It is a gradual form of hair loss where the hair follicles shrink over time.

This hair loss cause is determined by your genetics, meaning it is passed down by your family members.


Because pattern baldness gets worse as you get older, ageing is the main cause of hair loss. Noticeable hair loss usually starts affecting men in their 30s and 40s.

A man with thinning hair

Hair loss is a completely normal part of ageing for all men and women. Not only do your hair follicles produce finer hairs as you get older, but the rate of hair growth also slows down.

Hormonal changes

Changes in hormones have been linked to hair loss in men and women. For men in particular, this is to do with androgens (also known as sex hormones).

When androgens such as testosterone and DHT (dihydrotestosterone) change in the body, it can cause your hair follicles to shrink, leading to hair loss.

Medical conditions

Some health conditions include hair loss as one of the symptoms. Not every person with the following conditions will have hair loss, but it could be a possible cause.

  • Autoimmune diseases - conditions such as lupus can cause skin rashes which result in loss of hair if these rashes occur on the scalp.
  • Alopecia areata - this is a disease where your body's immune system attacks your hair follicles. This can sometimes cause you to lose all of the hair on your body, including your eyebrows and eyelashes.
  • Ringworm or other scalp infections - fungal infections such as ringworm can attack the scalp, specifically the top layer of skin where the hair follicles are.
  • Thyroid disease - this can cause the hormones in your body to become disrupted, affecting certain functions like hair growth.
  • Depression - being depressed has been linked to hair loss and hair thinning. Feeling low and fatigued can result in less hair growth, and the stress and anxiety that are associated with depression can also make your hair fall out.
  • Trichotillomania - this is a mental health condition. People who have this may pull out their hair when they are stressed or upset.
  • Eating disorders - psychological disorders such as anorexia and bulimia cause malnourishment, which stops the cells in your body from working as they should and can be a reason for hair loss.

External causes for hair loss


After a very sudden shock, the body can have sudden hair loss. This hair loss reason is called telogen effluvium.

Telogen effluvium might take place after:

  • a very stressful period in your life
  • the death of a loved one
  • some form of a traumatic event
  • pregnancy

With this type of hair loss, you might notice large portions of hair falling out simply by washing or brushing your hair.

Someone holding a hairbrush with lots of hair in it

However, hair loss due to stress isn’t permanent.

Lack of nutrients

A lack of certain nutrients in your diet can cause your hair to become brittle and fall out. If you suspect that your hair loss is due to unhealthy eating habits, try to increase your intake of:

  • zinc - found in poultry, red meat, beans, and dairy products
  • iron - found in liver, red meats, fish, or eggs
  • fatty acids - found in salmon and tuna

You can also take these nutrients in the form of supplements.

A diet that is very low in protein can also cause hair loss. If your body doesn’t have enough protein to repair itself, it will stop growing hair and use the protein for more important bodily functions.

Foods that cause hair loss

Foods aren’t generally a direct cause of hair loss. However, they can sometimes contribute to certain health conditions which might result in hair thinning or balding.

For example, eating too much sugar can lead to diabetes and insulin resistance (when your body’s cells don’t respond to insulin as they should), which can be a hair loss cause.

Heavy alcohol consumption is also bad for your hair, and could be another reason for hair loss. Your hair is mostly made up of a protein called Keratin, and alcohol can damage the production of this.


Some medications used to treat health conditions can cause hair loss as a side effect. In most cases, this type of hair loss is temporary and will only last during your treatment.

The following medications can cause hair loss as a potential side effect:

  • Anticoagulants - some treatments for blood clots such as Warfarin and Heparin can cause hair loss, mostly due to excessive hair shedding.
  • Cancer treatment - chemotherapy attacks growing cells to stop the spread of cancer, but in doing so also attacks the hair follicles. This often causes temporary hair loss.
  • Blood pressure medication - as a rare side effect, beta-blockers can cause hair loss and thinning hair.
  • Treatment for high cholesterol - statins are drugs that can lower your cholesterol. Hair loss is a rare side effect.
  • Epilepsy medication (anticonvulsants) - a study Trusted source PubMed Government Source Database of Biomedical Research Go to source on epilepsy medication showed alopecia (hair loss) to be the second most common side effect after weight gain.
  • Arthritis medication - a commonly prescribed medicine for arthritis called methotrexate can cause hair loss in a small number of its users.

Scalp burns or injuries

If you damage your scalp and your hair follicles, you will likely experience temporary hair loss.

Your hair should grow back fairly quickly unless your injuries have resulted in scarring. If this is the case, the hair follicles will have been destroyed, causing permanent hair loss.

Vitamin deficiencies

A lack of vitamin B could play a role in hair loss, specifically B2, B7, B9, and B12. Eating a healthy diet including meat, fish, eggs, and dairy products should help you get enough of this vitamin.

If you do not eat animal products you could take a vitamin B supplement once a day.

Female hair loss

Some hair loss causes are specific to women only. You are more likely to suffer from hair loss if you:

  • Are menopausal or perimenopausal - hormone changes that take place during and leading up to menopause can result in hair loss. Taking hormone replacement therapy (HRT) could slow down or even stop menopausal hair loss.
  • Have recently given birth - childbirth is an extreme shock for many women, causing lots of stress to the body. This can result in sudden hair loss after pregnancy.
  • Frequently style your hair or use products - bleaching, perming, and using heat or multiple products can make hair brittle, leading to hair damage and hair loss.
a range of hair products on shelves


Hair loss has many causes, but is mostly a result of your genetics and is a natural part of ageing. Other causes include hormonal changes, stress, as well as medical conditions and treatments - but in these cases, hair loss is usually temporary.

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