Hair Growth Cycle
Human hair has a growth cycle with 3 phases: anagen, catagen, and telogen. The anagen, or “growth” phase can last up to 8 years and accounts for nearly 90% of the hair you see on the scalp at any given time. The hair follicle will shrink during the catagen phase which lasts between 2-3 weeks. Lastly, the hair follicle rests for a few months during the telogen phase.
With 90% growing at any given time, only about 10% of our hair is shrinking or resting each day. Other than hair breakage which can certainly lead to hairs being left in the brush, on clothes and in the drain, hairs that fall out each day are expected, but not in large or increasing numbers. Women with hair loss may see a larger amount of hair than before left in their hairbrush or on the pillow in the morning. They typically see space at the crown and hair part in the middle and front of the scalp. Visualizing more scalp than usual at the temples and hairline is also a common sign of hair loss in women. Though men will tend to see hair recede following a horseshoe pattern- retaining the sides and back- women most commonly see mild to moderate thinning at the top of the head while keeping a sparse hairline intact.
Many possible culprits can cause temporary female hair loss, while some are permanent.
Androgenetic alopecia is a hereditary condition affecting an estimated 30 million American females, or 50% of women by the time that they are 50 years old.
Family History & Hair Loss
This condition, which will tend to show up in family history as well, is characterized by hairs that fall out and are replaced with thin, finer hairs until the follicles shrink so much they regenerate no hairs at all. Hair which once felt strong and robust can become wispy and break easily. Looking closely at the scalp through a microscope reveals hair follicles that vary in size and indicate this genetic predisposition.
Conversely, when a close-up glance reveals that hairs and follicles are all roughly the same size, sudden hair shedding, or baldness is more likely to be related to a temporary, non-hereditary cause such as medication, stress or a health concern. Telogen effluvium, is a medical term for temporary, dramatic hair loss related to temporary triggers.