Causes of hair loss 

Each type of hair loss has different causes, although the causes of some types are poorly understood.

Male- and female-pattern baldness

Male-pattern baldness is hereditary, which means it runs in families. It is not clear if this is the case with female-pattern baldness.

Male-pattern baldness is thought to be caused by oversensitive hair follicles (holes in the skin that contain the roots of each hair). This is linked to the hormone dihydrotestosterone (DHT), which is made from the male hormone testosterone.

If there is too much DHT, the follicles react to it. The hair becomes thinner and grows for a shorter length of time than normal. The balding process is gradual because different follicles are affected at different times.

The causes of female-pattern baldness are less well understood. Women who have been through the menopause may have an increased chance of female-pattern baldness because they have fewer female hormones.

Alopecia areata

Immune system imbalance

Alopecia areata is an autoimmune condition. The immune system is the body's natural defence system, which helps protect it from infection by bacteria and viruses.

Usually, the immune system attacks the cause of an infection, but in the case of alopecia areata it damages the hair follicles instead. It is not clear exactly why this happens. Fortunately, the hair follicles are not permanently damaged and in many cases the hair grows back within a few months.

Alopecia areata is more common among people with other autoimmune conditions, such as:

  • thyroid disease – conditions that affect your thyroid gland, such as an overactive thyroid (hyperthyroidism) 
  • diabetes – a condition caused by too much glucose (sugar) in the blood 
  • vitiligo – a condition that produces white patches on the skin

Alopecia areata is also more common among people with Down syndrome, a genetic condition that causes learning difficulties and affects physical development. More than one in 20 people with Down syndrome have alopecia areata.


Some people may be genetically more vulnerable to alopecia areata. Certain genes (units of genetic material) may make the condition more likely.

Around one in five people with alopecia areata have a family history of the condition, suggesting that the tendency to develop the condition may be inherited. You may also be at an increased risk of alopecia areata if a member of your family has one of the autoimmune conditions mentioned above.

Scarring alopecia

Scarring alopecia is caused by permanent damage to the hair follicles. In many cases, it is not clear why this happens, although it is sometimes the result of another condition.

Conditions that can cause scarring alopecia include:

  • scleroderma – a condition that affects the body's connective (supporting) tissues, resulting in hard, puffy and itchy skin
  • lichen planus – a non-infectious, itchy rash that can affect many areas of the body
  • discoid lupus – a mild form of lupus that affects the skin, causing scaly marks and hair loss
  • folliculitis decalvans – a rare form of alopecia that most commonly affects men, causing baldness and scarring of the affected areas  
  • frontal fibrosing alopecia – a type of alopecia that affects post-menopausal women where the hair follicles are damaged, and the hair falls out and is unable to grow back

Anagen effluvium

Anagen effluvium is usually caused by medical treatments for cancer, most commonly chemotherapy.

However, not all chemotherapy drugs cause hair loss and sometimes the hair loss is so small it is hardly noticeable.

In some cases, other cancer treatments – including immunotherapy and radiotherapy – may also cause hair loss.

Telogen effluvium

Telogen effluvium is a type of temporary hair loss that can be caused by your body reacting to:

  • hormonal changes, such as those that take place when a woman is pregnant 
  • intense emotional stress
  • intense physical stress, such as childbirth
  • a short-term illness, such as a severe infection or an operation 
  • a long-term illness, such as cancer or liver disease
  • changes in your diet, such as crash dieting 
  • some medications, such as anticoagulants (medicines that reduce the ability of your blood to clot) or beta-blockers (used to treat a number of conditions, such as high blood pressure)   

Cancer treatment: coping with hair loss during chemotherapy

Hair loss is a potential side effect of chemotherapy. Jessica, who was diagnosed with breast cancer in 2009, talks about her experience with chemotherapy and describes how the hair loss affected her. Also, an expert gives advice on how to cope with hair loss and where to find support.

Media last reviewed: 19/07/2014

Next review due: 19/07/2016

Women and hair loss: coping tips

Losing your crowning glory can be particularly difficult for women. But there are ways to cope

Page last reviewed: 12/11/2012

Next review due: 12/11/2014