what can cause hair to fall out


There are many conditions that contribute to different types of hair loss in women.  Some of the most common triggers of hair loss include autoimmune diseases, dermal conditions such as seborrhoea dermatitis, thyroid disease and polycystic ovary syndrome (PCOS).  Other factors that can interfere with the hair growth cycle include illness, infection and some types of prescription medication.


Hair grows in three distinct cycles: anagen, catagen and telogen.  At any one time approximately 90% of hair follicles should be in anagen phase.  Anagen phase (or growth phase) should last between 2 and 8 years.  At a growth rate of 0.5 inches per month, it should take around 3 years to grow your hair 18 inches long.

Only 10% of the hair on the scalp should be in telogen phase.  In telogen stage, the hair has transitioned out of anagen stage and will rest for 2-3 weeks before shedding.  Hair loss will start to become evident when more than 30% of the hair is in telogen stage.  With an increased number of hairs in telogen phase, hair shedding will increase and appear not to grow any longer.  To regrow hair, the anagen / telogen balance must be restored.


Hair shedding is a normal part of life and in most cases, it is totally normal.  On average, we can expect to lose about 80 strands of hair a day.  when this level of shedding increases or you start to notice your parting is wider, it is likely you are experiencing hair loss.  Reactive hair loss is also known as telogen effluvium.  If this type of hair loss continues over a sustained period it is classed as chronic telogen effluvium [1].

There are many common triggers of reactive hair loss:

  1. Family history of hair loss – We all know genetics play a role in hair loss, but our genetic material does not always dictate our fate.  If you have a family history of thinning hair, it is useful to identify other common contributing factors to hair loss that also run in the family such as anaemia, cardiovascular disease or diabetes.
  2. Hormonal changes – Changes in levels of androgens and estrogens can lead to a range of frustrating and aesthetically displeasing health issues such as adult acne and abdominal weight gain.  If your hormones are out of balance, you may also notice excess hair on your chin and on your stomach due to higher levels of DHT.  Increased levels of DHT are known to contribute to female pattern hair loss (androgenic hair loss), DHT can also contribute to the reduced growth and increased shedding that is commonly seen in telogen effluvium when there is a mild increase in the DHT / testosterone ratio.
  3. Stress and starvation – Stress increases glucose levels and leads to a number of metabolic changes in the body.  Cortisol is a catabolic hormone that prevents growth and promotes the breakdown of tissue and collagen to provide an immediate source of fuel for the body.  Cortisol levels are normally highest in the morning and drop after breakfast.  Calorific restriction or fasting will also increase cortisol.  When going through stressful periods, try to avoid skipping meals and focus on proteins to keep blood sugar levels stable.  Never skip breakfast and indulge in relaxing activities such as mediation, yoga or anything that takes your mind off pressing issues.
  4. Vitamin + mineral imbalance – A number of nutrients are essential for healthy hair.  One of the most common causes of hair loss is iron deficiency, iron is crucial for the production of proteins that make up the hair fibre and without it your hair will suffer.  Other important nutritional components that are essential for hair growth include B-complex vitamins, zinc and potassium.
  5. Medication + medical conditions – Some medical conditions such as hypothyroidism and PCOS are major triggers of hair loss.  High and low levels of thyroid hormone are linked to slower hair growth and the hormone imbalances that make up the clinical features of PCOS can have a marked effect on hair follicle cycling.  Many different drugs are known to contribute to hair loss.  These medications include: antibiotics, anti-fungals, acne medication, cholesterol lowering drugs, antidepressants and immunosuppressive agents.


Hair loss is frequent in women in their forties, thirties and even their twenties.  Some types of hair loss are due to genetic factors that are triggered due to environment or nutrient imbalances, whilst other types of hair loss are triggered by medical conditions.  Most types of hair loss can be reversed if the condition is investigated and the trigger is identified and removed.  Once the cause of the hair loss has been isolated and removed, normal hair growth should be removed.


  1. Liyanage, D. and Sinclair, R., 2016. Telogen effluvium. Cosmetics, 3(2), p.13.