Hair loss isn't straightforward. It affects men, women, teenagers and even young children - everyone is at risk, no matter what their age or physical make-up. But there isn't one clear cause – a number of different factors may be responsible for hair loss.

Surgery and illness can cause hair to fall out, sometimes several months after the event due to dietary issues or stress.  After a major illness or surgery, the body sometimes lacks the food or vitamins it needs - and if people are on a low-protein diet, the body enters a resting phase of hair growth. Certain medications can also cause hair loss, as well as high doses of vitamin A.

Cancer treatments such as chemotherapy and radiation treatment prevent hair cells from dividing, thinning and weakening hair as it emerges from the scalp. It's not permanent, though, and the hair grows back after treatment.

Alopecia Areata sounds like a mouthful, but describes a condition 1-2 per cent of the population, male and female. It's sometimes known as spot baldness because of the bald spot patterns it causes on the scalp. Alopecia doesn't only affect the hair on your scalp, though - a variant can cause your to lose facial hair. Celebrity Gail Porter suffers from the condition. In 90% of cases, the hair will eventually grow back - although it can take more than a year to do so.

But it's not just medical issues that cause hair loss – damage can be done to the hair through neglect, or even through being too attentive to your hair. Some treatments have powerful chemicals in them, and overuse or incorrect use can cause the hair to become brittle and break away. Certain types of styling, such as braids can also increase the amount of stress on the hair and mental health issues such as hair pulling (or trichotillomania) can result in self-inflicted hair loss.

If you think you may be suffering from any of the above problems, it's best to discuss it first with your doctor to determine what course of action to take.

More reading:

http://hairlosshelp.com/hair_loss_research/hairloss_causes.cfm
http://www.dailymail.co.uk/health/article-362256/Alopecia-What-need-know.html
http://familydoctor.org/online/famdocen/home/men/general/081.html
http://www.bbc.co.uk/health/womens_health/body_hairloss.shtml