Hair loss

• We each have about 100 000 hairs on the scalp
• It is normal to lose 50–100 hairs from the head each day
• Each hair on the head grows for about 5 years before being shed
• Eyebrow hairs grow for only 10 weeks
• Scalp hair grows at a rate of about 1 cm (just under half an inch) a month
• A survey has shown that about 7.9 million men and 1.6 million women in the UK have hair loss problems
• Each year, American men spend about $900 million on efforts to regrow hair
• In the USA and UK, there has not been a bald President or Prime Minister since the television age began

Hair loss is a big worry to many people, both male and female. If you have a worrying amount of hair in the basin after shampooing, you may think you are on the way to baldness. But this is not usually the case. The 50–100 hairs that everyone loses each day often become tangled with the rest of the hair, but are washed out when we shampoo. So we see what seems like a lot of hair in the basin after shampooing, but in reality these hairs have been shed earlier.

Of course, bald areas are an obvious sign of hair loss, but otherwise it can be difficult to tell whether your hair is getting thinner. To find out, try the ‘tug test’. Hold a small bunch of hair – about 15 or 20 hairs – between the thumb and index finger. Pull slowly and firmly. If more than six hairs come out there may be a problem.

How hair grows
The portion of the hair that we can see is called the shaft. Each shaft of hair protrudes from its follicle, which is a tube-like pouch just below the surface of the skin. The hair is attached to the base of the follicle by the hair root, which is where the hair actually grows and where it is nourished by tiny blood vessels.

Like the rest of the body, hairs are made of cells. As new cells form at its root, the hair is gradually pushed further and further out of the follicle. The cells at the base of each hair are close to the blood supply and are living. As they get pushed further away from the base of the follicle, they no longer have any nourishment and so they die. As they die, they are transformed into a hard protein called keratin. So, each hair we see above the skin is dead protein. It is the follicle, which lies deep in the skin, that is the essential growing part of the hair.

The thickness of each hair depends on the size of the follicle from which it is growing. At puberty in boys, hormones increase the size of the follicles on the chin, chest and limbs so that each hair becomes more thick and wiry. In the elderly, the follicles shrink and the hair becomes finer.

Stages of hair growth
Hair growth is not a continuous process. It has several stages.

• The first phase is the growing stage. Hair grows at about 1 cm each month, and this phase lasts for anything between 2 and 5 years.
• This is followed by a resting stage, during which there is no growth. This phase lasts about 5 months, and is called telogen.
• At the end of the resting phase, the hair is shed and the follicle starts to grow a new one.
• At any moment, about 90% of the hair follicles of the scalp are growing hairs in the first phase; only about 10% are in the resting phase.
• If a follicle is destroyed for any reason, no new hair will grow from it.

What happens to cause baldness
Excessive hair loss can occur if any of the stages of hair growth become disrupted. For example, if follicles shut down (meaning that they stay in the resting phase and then shed the hair) instead of growing new hairs, there will be less hair on the head.
Another reason might be interference with the formation of new hair cells at the root during the growing phase; this occurs with some anticancer drugs. If follicles have been destroyed (as they might be by, for example, a burn or by some skin diseases), there will be baldness in that area.

An individual can also look bald if the hairs are growing but are so fragile that they break just as they emerge from the follicle, or if they are very small and thin.

In 1998, scientists at Columbia University in New York announced the discovery of a gene that appears to be the ‘master switch’ for hair growth. They found the gene after comparing the genes of hairless mice belonging to a mutant breed, and comparing the genes of 11 members of the same family who had lost all their hair. This discovery is a step towards understanding how the hair follicle works and how baldness happens, and may lead to effective treatments in the future.

Common beliefs – true or false?

‘Some hairstyles can cause hair loss’
True. Styles that put tension on the hairs – such as tight ponytails, plaits or corn-rows – can cause hair loss. Winding hair tightly onto rollers (particularly heated rollers) can have the same damaging effect.

‘Brushing the hair 100 times a day will stimulate the circulation and prevent hair loss’
False. Vigorous brushing is more likely to injure the hairs and make the problem worse.

‘Hair needs to breathe, so wigs and toupees worsen loss of hair’
False. Hair does not need to breathe. Only the root of the hair is alive and this gets its oxygen from the blood in the scalp. Wigs and hairpieces will damage hair only if they are too tight.

‘Frequent shampooing makes hair fall out’
False. Shampooing simply gets rid of the hairs that have already fallen out.

‘Blow-drying and heated brushes can worsen hair loss’
True. The reason is that extreme heat damages the proteins in the hairs, making them fragile and liable to break off. Brushing the hair during blow-drying causes more damage. Careless use of heated brushes can even burn the scalp, so that the hair follicles are permanently damaged in that area.

‘Protein-containing conditioners and shampoos nourish the hair and help it to grow’
False. Protein-containing conditioners only temporarily fill in defects on the surface of the hair shaft, making it smoother and thicker.

‘Hair dyes, perms and hairsprays worsen hair loss’
False. Hair dyes, perms and hairsprays do not affect thinning hair. Perms and hairsprays can help to disguise the problem.

‘If your father has a full head of hair, you will not go bald’
False. A tendency to baldness is inherited and probably involves a combination of genes. So you are not automatically in the clear even if your father has a full head of hair. It is not true, as sometimes claimed, that only genes from the mother’s side are involved.

‘Baldness means that you are more likely to have a heart attack’
Partly true. In 1999, doctors at Harvard Medical School found that men who had lost hair at the crown of the head had a 32% increased chance of coronary heart disease. Hair loss at the front of the head (a receding hairline) hardly increased the risk at all. So if you have baldness at the top of your head, you should stop smoking, eat healthily, have your blood pressure checked and do some exercise.

‘Low levels of zinc in the body are a reason for hair loss’
Probably false. There is no evidence that low zinc levels cause hair loss in people taking a balanced diet or that zinc supplements improve hair loss.

‘Stress can cause hair loss’
True. Scientists have now identified some chemicals that are produced in the body during periods of stress, which can affect hair growth (Journal of Investigative Dermatology 2004;123:455–7).

‘It is normal to lose hair from our early 30s’
True. A person aged 20–30 years typically has 615 hair follicles per square centimetre. The number falls to 485 by 50 years of age and to 435 at 80–90 years of age. Also each hair is thinner. So, with ageing, hair becomes both finer and sparser.