First, a bit about hair
Hairs are tiny shafts of a protein called keratin. They are anchored in a group of specialised cells called hair follicles, which supply oxygen and nutrients to the root (or bulb) of the hair, and lubricate the hair with an oily substance called sebum.
The human body is completely covered with hair follicles, except on the palms of the hands, soles of the feet and the lips. Mostly, hair follicles are tiny, and the hairs they produce don’t grow long enough to protrude from the pore.
The areas where hairs do protrude (and are visible above the skin) include the armpits, face, around the genitals, the front of the chest, the back, and most profusely, on the scalp of the head. A scalp typically contains about 100,000 hair follicles.
Hair is in a constant cycle of growth, rest, and renewal. Hairs grow and then are shed, but because they grow at different rates they don’t all shed at once.
It takes about three years for hair follicles to produce a hair that grows, rests, falls out and then regrows, which means the scalp loses between 50 and 200 hairs a day.
When men start to go bald
In some males, the hair growth process slows right down.
The growth phase of each hair gradually becomes shorter, and the resting phase becomes longer. Eventually the hairs that are growing become so short that they barely emerge from their hair follicle.
The process begins at the sides of the head (above the temples) and at a patch on the crown, and spreads from there. As the hairline recedes backwards, the patch gets larger too.
This is known as male “pattern baldness”, or androgenetic alopecia. It’s the most common type of baldness, affecting about half of all men by the age of 50 and more than 80 per cent by the age of 70.
What about women?
Women get pattern hair loss too, but it’s less common than in men (though it’s still the most common cause of hair loss in women).
The pattern of hair loss is different, however: it tends to thin over the top of the scalp rather than result in a patch of baldness, dermatologist Michael Freeman of Bond University says.
“Often in females it will affect 50 per cent of their hair, so many women will not go truly bald, but their hair can get so perilously thin that it can become a big problem for them,” Associate Professor Freeman says.
Over 50 per cent of women have some mild hair loss as they age, and about 20 per cent of women develop moderate or severe hair loss.