Hair loss refers to a loss of hair from the scalp or body. The medical term for hair loss is alopecia. There are many different causes of alopecia, some permanent, others temporary. Hair loss is more common in men, affecting 60% of men and up to 40% of women.
Hair is composed of a protein called keratin. Hair grows everywhere on our skin, except for on our palms and the soles of our feet. The average adult head grows about 100,000 to 150,000 hairs, and 80 to 100 are normally shed each day. At any one point in time, around 90% of the hair on the scalp is growing. This is known as the anagen phase. There are three main phases of hair growth:
Anagen phase. On average hair grows 0.3-0.4 mm/day or around 12-15cm per year, although this is genetically predetermined. As people age, their rate of hair growth slows. The hair root looks long, white, and tapered during this phase
Catagen phase. Hair growth stops during this phase and the hair root starts to shrink and become rounded. This phase may last from two to three weeks
Telogen phase. This is also called the resting stage. The hair root is now fully rounded, and awaiting the growth of a new anagen hair to push it out of the scalp so it can be shed. This phase lasts around three to four months for scalp hair.