What causes it?

When hair loss is described as "male-pattern" or "female-pattern", it is genetically determined, said Dr Derrick Aw, a consultant dermatologist at the National University Hospital. Such hair loss is common.

However, non-genetic external factors like hair styling may also play a part.

"Excessive hair treatment, such as the use of hot curlers, may also cause hair to become fragile," he said.

Dr Pang Shiu Meng, the head of the dermatology department at the Singapore General Hospital, said that hair loss may occur after major health events such as surgery, a severe illness or after giving birth.

The result - a sudden onset of bald patches.

"Your hairdresser is usually the one who will discover the bald patches," said Dr Pang. "Occasionally, other parts of the body, such as the beard in men, may be affected."

Medical conditions like thyroid disorders are linked to hair loss. There is also trichotillomania, a condition in which one has an uncontrollable urge to pull out hair to relieve stress. It usually affects young girls and their parents may not be aware of it, said Dr Pang.

What you can do?

Unfortunately, treatment for hair loss is lifelong, said Dr Aw. Topical products such as Regaine contains minoxidil, which is effective for treating hair loss. One has to apply and massage the product into the scalp as directed.

However, people who do not respond well to treatment or are at an advanced stage of hair loss may consider surgical alternatives such as hair transplants, said Dr Pang.

Dr Aw added that alternative treatments for hair loss, such as herbal treatment, are not validated by clinical trials, so their effectiveness is unproven.

As for bald patches and hair loss induced by illness or giving birth, hair will usually regrow in a few months' time. Bald patches can also be treated with hormone injections, although the regrown hair may be white, said Dr Pang.
 
Is it worth seeing a doctor?

Men may want to approach their doctor for a prescription drug called Propecia, which specifically treats male-pattern hair loss, said Dr Aw.

This article was first published in Mind Your Body, The Straits Times.