Our hair is constantly falling out and growing back again.
The average person loses between 50 and 100 hairs from their head each day, but this is completely normal.
It is only when the balance of hair loss and hair regrowth goes awry that we start to refer to it as baldness but why do some people go bald and is it only men that do?
We have an average of 100,000 to 150,000 hairs on our scalp at any one time each, at a different stage of the growth cycle.
Hair growth is controlled by hair follicles located within our skin.
They are miniature organs creating a complex network that was formed before we were even born. Hair grows in cycles of three phases.
First there is the growth phase, called the anagen phase. The second phase is the regression, or catogen phase and this is when the hair follicle causes the hair to shrink.
The final phase is the resting, or telogen phase.
This cycle of growth is often influenced by different internal and external factors such as changes in hormone levels, stress, health and medical treatments; usually returning to normal once these factors change.
Many men find that, as they age, the hair growth on their heads starts to alter.
This is because the hair follicles responsible for the growth cycle become more sensitive, often to one particular hormone, called Dihydrotestosterone, DHT.
The most common type of baldness in men is male pattern baldness, accounting for up to 95% of balding in men and estimated to affect about 80% by the age of 80.
Male pattern baldness typically follows a specific pattern. It begins with a receding hairline at the temples.
The hair of the crown then begins to thin.
The hair loss continues until hair is left only around the sides of the head, the typical horseshoe growth pattern.
Scientists are still discovering how and why baldness occurs.
It would seem that the heightened sensitivity of specific scalp follicles to DHT causes the hair growth to slow down and the hair to thin.
DHT appears to make these hair follicles shrink resulting in much shorter and wispier hair.
These areas of the scalp are not actually completely bald, the hair is usually just so short and thin it is hard to see.
A number of genes have been associated with baldness, it is usually inherited but it is a complex genetic process that causes it.
There are many different types of hair loss, not just male pattern baldness, although it is the one we are most familiar with; and hair loss is not just an issue for men, women can experience it too.
Many women will experience temporary changes in their hair growth cycle due to significant hormonal changes such as pregnancy, childbirth and menopause.
The number of known genetic hair disorders number in their hundreds; some, like alopecia universalis can lead to complete hair loss over the entire body.
There is also a female pattern hair loss which is more commonly presented as thinning of the hair rather than full hair loss.
So although we more commonly associate baldness with men, women can certainly be affected too.