Many people have found themselves holding clumps of hair in their hands during a shower and can’t think of the cause. Maybe you’ve been experiencing some stress in recent months, but it’s over now – so why suddenly is your hair falling out?
Why does hair loss occur only months after a trigger event?
The answer to this lies in the life cycle of a strand of hair.
The first phase of hair growth is the anagen phase. This phase lasts between 3-5 years, with each strand growing approximately half an inch per month. The growth phases of hairs on other places of the body are shorter, for example the eyelashes have a growth phase that lasts 30 days.
The second phase or catagen phase is a more transition phase which has a duration of about 10 days.
Next comes the telogen phase, also known as the resting phase.
Exogen occurs when the hair falls out of the scalp. The remaining follicle is inactive for about three months before the whole process begins again.
At any given moment, every strand of hair is at a different point in its life cycle.
A sudden loss of an abnormal number of hair strands occurs when there is a disturbance in the normal life cycle.
Remember that it is normal to lose about 80 strands on average, per day, in a healthy individual.
What stressful events can precipitate hair loss?
There are a number of stressful events that can cause hair loss. Here are just a few examples:
- A bereavement
- Major upheaval such as a house move
How does stress cause hair loss?
During the stressful event (stressor), the effect on the hair cycle can result in the growth (anagen) phase being cut short. This can lead to many hair strands entering the telogen phase, then the exogen phase- all at the same time.
A consequence of constant exposure to the stressor will result in hair that will never be in the growth phase long enough to achieve optimum length. Your hair won’t grow as long as it used to prior to the stress.
The exact cause of precipitating the hair cycle into the telogen phase is believed to be due to the hormones or neurotransmitters released in the body in response to the stressor. A study done on monkeys found that those subjects with more cortisol (a stress hormone) in their hair were more prone to hair loss.
Even women who have recently given birth experience this hair loss. Once the hormone levels drop after the birth, shedding of hair accelerates.
It is usually three months after the body experienced the stress, that the excessive hair shedding occurs. This coincides with the added duration of the catagen and telogen phases- when the hair ceases growing and when it sheds.