One of the commonest forms of hair loss in men and women is a condition called telogen effluvium, in which there is a widely spread out shedding of hairs around the scalp and elsewhere on the body. This is an allover thinning of the hair, rather than patches of baldness.

Telogen effluvium is usually a reaction to intense stress on the body’s physical or hormonal systems, or as a reaction to medication.

The condition generally begins suddenly, with no warning, and gets better on its own within about six months, although in some circumstances it can become a chronic problem.

Because telogen effluvium develops a while after its trigger, and causes generalised thinning of hair density rather than a bald patch, women with the condition can easily be diagnosed as overanxious or neurotic. Fortunately, it often gets better with time.

Hair growth cycles alternate between a growth phase (called anagen, it lasts about three years) and a resting phase (telogen, which lasts about three months). During telogen, the hair remains in the follicle until it is pushed out by the growth of a new hair in the anagen phase.

At any one time, up to about 15 per cent of hairs are in telogen. But a sudden stress on the body can trigger large numbers of hairs to enter the telogen phase at the same time. Then, about three months later, this large number of hairs will be shed. As the new hairs start to grow out, so the density of hair may thicken again.

Many adults have had an episode of telogen effluvium at some point in their lives, reflecting episodes of illness or stress.