The science behind hair loss

What causes hair loss?

This is possibly the question we are asked the most.  Hair loss can be due to a number of factors but by far the most common is Androgenetic Alopecia (hereditary pattern baldness) in men. Up to 50% of men will experience hair loss by the age of 50.

This can also be seen in the female population but follows a different pattern and is not as common.  It is well known that hair loss has both physical and psychological implications.

The science behind androgenetic alopecia

Genes play an important role in determining the extent of hair loss.  Think of it as a genetic susceptibility to hormones.  
Dihydrotestosterone (DHT), a product of Testosterone, can cause these follicles to shrink over time and eventually lead to the hair falling out. This usually occurs in a “pattern” that is well recognised. One of the reasons we harvest hair from the back of the head during hair transplant surgery is due to the strong likelihood that these hairs are outside of the pattern and much more likely to be permanent.

Medication such as Finasteride plays an important role in countering the effects of DHT on these follicles and can stabilise ongoing hair loss, in some cases, it can be reversed. Family history is a strong predictor of hair loss progression.

Stages of male pattern baldness

1. Temples

Hair starts to recede in the hairline and temples creating an elevated angle or a defined "widows peak"

2. Crown

Thinning and loss in the crown and/or vertex regions - this can be independent or often as a combination with recession

3. Patchy or Diffuse Loss

Hair may be seen to thin in patches which often conform to a "pattern" and join up as the loss progresses.  This may be independent or combined with diffuse loss where the hair on the entire scalp begins to thin and can be more prominent in these patches.

4. Moderate Pattern Loss

Most of the hair on top of the head including the crown has thinned significantly - any remaining hairs are very thin

5. Extensive Pattern Loss

Almost all of the hair on top of the head has been lost at this stage, usually leaving a defined area around the back and sides - these hairs are more resistant to hormonal influences

6. Complete

The top of the head and crown are usually completely bald, often at this stage the remaining hair around the back and sides appears to be thin and is limited.

The psychological impact

The impact that hair loss has on confidence and self esteem is often overlooked. In one poll it was found that almost half (47%) of hair-loss sufferers would spend their life savings to regain a full head of hair.  Our patients see a significant improvement in their quality of life after successful treatment and find that they can enjoy their life to a fuller potential without being as concerned about their hair loss.

¹Combined treatment with oral finasteride and topical minoxidil in male androgenetic alopecia, 2015
² Finasteride: a review of its use in hair loss, 2012
³Global photographic assessment of men... Olsen, 2007

Other causes of hair loss

Telogen Effluvium

Telogen effluvium is a form of temporary hair loss that occurs when a large number of hair follicles shift from the growth phase (anagen) to the resting phase (telogen) prematurely. Normally, about 80-90% of your hair is in the growing phase, while 10-20% is in the resting phase. Telogen effluvium disrupts this balance, causing more hair to enter the resting phase and eventually fall out.

This condition is often triggered by significant physiological or psychological stressors, such as:

  1. Physical Trauma or Illness: Major surgery, chronic illness, or severe infections can contribute to telogen effluvium.
  2. Hormonal Changes: Events like childbirth, discontinuation of birth control pills, or the onset of menopause can influence hormonal levels and contribute to hair loss.
  3. Emotional Stress: Intense emotional stress, grief, or a traumatic event can be a trigger.
  4. Nutritional Deficiencies: Poor nutrition or rapid weight loss may lead to telogen effluvium.
  5. Medications: Certain drugs, like anticoagulants, beta-blockers, retinoids, and some antidepressants, can contribute to hair loss.

The characteristic feature of telogen effluvium is diffuse shedding of hair rather than specific bald patches. Hair loss usually becomes noticeable several months after the triggering event. The good news is that telogen effluvium is often reversible, and hair typically regrows once the underlying cause is addressed or the stressful event passes.

Alopecia Areata

Alopecia areata is an autoimmune disorder causing sudden hair loss, typically in patches on the scalp. It results from the immune system mistakenly attacking hair follicles. In severe cases, it can lead to complete baldness on the scalp (alopecia totalis) or loss of all body hair (alopecia universalis). While there's no cure, some treatments aim to modulate the immune response and promote hair regrowth.

Burns and scars

Burns both chemical and physical can cause areas of hair loss.  Scars from injuries or surgery also lead to hair loss within the scar tissue.  Hair transplant surgery can be used to successfully treat areas of loss in scar tissue.

Traction Alopecia

Traction alopecia is a form of hair loss caused by prolonged tension or pulling on the hair. It commonly occurs due to tight hairstyles, such as braids, ponytails, or extensions. The constant pulling damages the hair follicles, leading to gradual hair loss, especially along the hairline or in areas subject to repeated tension. Prevention involves avoiding tight hairstyles, and early intervention may allow for hair regrowth.


Trichotillomania, commonly known as "trich," is a mental health condition where individuals feel an uncontrollable urge to pull out their hair, resulting in noticeable hair loss. This behaviour can occur in different areas where hair grows, like the scalp, eyebrows, or eyelashes. Trichotillomania is categorised as an impulse control disorder and is often linked to obsessive-compulsive disorder (OCD).People with trichotillomania may pull their hair as a way to deal with stress, anxiety, boredom, or other negative emotions. Although pulling out hair might bring a sense of relief or satisfaction, it is often followed by feelings of guilt, shame, or distress.Trichotillomania can significantly affect a person's emotional well-being and may lead to physical consequences, such as skin damage or infections if the hair-pulling is severe. Treatment typically involves a mix of therapeutic approaches, including cognitive-behavioural therapy (CBT) and habit reversal training. Medications may also be considered in some cases.

Skin Conditions

Skin issues like eczema, psoriasis, scarring, and infections in specific areas can lead to either temporary or permanent hair loss. In cases of permanent hair loss, we provide various surgical options to restore hair in areas where the underlying skin problem has been successfully treated or has become inactive.


Many chemotherapy drugs combat cancer by disrupting the growth of cancer cells, but unfortunately, they may also impact normal cells, including hair follicles. Wearing a 'cool cap' during chemotherapy can potentially reduce hair loss by limiting the drugs' impact on the scalp. Thankfully, in most cases, hair tends to regrow after completing chemotherapy.

In radiotherapy, hair loss is confined to the treated area. While regrowth isn't guaranteed after radiotherapy, we are available to discuss available options. It is recommended to consult with your GP, specialist nurse, or cancer support specialist before taking any action, as coordination with them may be necessary

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