, hair loss, baldness, alopecia, disease, and treatment information

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Hair Biology
Diagnosis / Decisions
Androgenetic Alopecia Biology
Androgenetic Alopecia Clinical Patterns
Androgenetic Alopecia Treatments
Hair Restoration
Alopecia Areata
Scarring Alopecias
Inflammatory Alopecias
Other Alopecias
Hair Shaft Defects
Infectious Hair Disease
Hirsutism / Hypertrichosis
Hair Color
Hair Cosmetics
Bits and Pieces
  • You shed more hair in the fall and spring than in summer and late winter in response to the changes in seasons and daylight exposure.
  • Asian men have little beard growth and a lower risk of developing androgenetic alopecia as, on average, they produce less testosterone than Caucasians.
  • On average, each person has 20 million hair follicles of which 90,000 to 140,000 are scalp hair follicles.
  • You can lose up to 25% of your scalp hair before it becomes noticeable.
  • Typically, scalp hair fibers grow for two to seven years before being replaced by a new hair fiber.
  • On average, healthy adult scalp hair fibers grow at 0.35mm per day.
  • Eyelashes are the slowest growing hair fibers at less than 0.16mm per day.
  • Chin hairs on young adult males are the fastest growing hair fibers at up to 0.42mm per day.
  • Women have a faster rate of hair growth on their scalps compared to men by about 0.02mm more per day.
  • The world's most expensive shampoo is arguably Alterna shampoo which contains caviar and costs $200 a bottle. Alterna is a favorite of the rich and famous and claims to have age-defying properties.
  • Rate of hair growth declines with age. As a child, scalp hair grows at up to 0.41mm per day, but that drops to 0.32mm per day in old age.
  • Over $1.6 billion is spent in the US each year on treating hair loss.
  • Hair fiber is as strong as copper wire of the same diameter. It has a tensile strength of around 1.6 x10-9 N / m2 (one point 6 times ten to the power minus nine newtons per meter square of hair cross section diameter).
  • Up to $180 million of minoxidil is sold each year.
  • Over 70 million people in the US have some degree of androgenetic alopecia.
  • Normally, dry hair can be stretched one-fifth of it's length before breaking. Wet hair can stretch between 40-50% of it's length.
  • On the scalp there is an average of 1,000 hairs per square inch or about 250 hair fibers per square centimeter.
  • People without alopecia may lose up to 100 scalp hairs a day as a result of normal hair cycling.
  • The fine, downy hair that covers the cheeks and other parts of the face is called lanugo hair. The hair on your scalp and any other body hair that is pigmented is called terminal hair.
  • The numbers of hairs on the head vary with the hair's natural color. Redheads have about 90,000. Black, 108,000, while brown and blonde haired people have up to 140,000. The number of scalp hairs changes with ethnicity too. Far east Asians have as few as 80,000 scalp hair follicles.
  • In terms of raw elements, on average, hair is composed of 50.65% carbon, 20.85% oxygen, 17.14% nitrogen, 6.36% hydrogen, and 5.0% sulfur. Hair also contains trace amounts of magnesium, arsenic, iron, chromium and other metals and minerals.
  • Darker hair contains higher levels of carbon than blonde hair.
  • Between 65% and 95% of hair fiber is made of proteins called keratins. Keratins are made from amino acids and in hair keratins the predominant amino acid is cysteine.
  • One keratin protein molecule measures 10 nanometers across. 10,000 keratin protein molecules lying side by side cover the width of one human hair. So the cross section of one human hair can contain up to 78,000,000 keratin proteins.
  • The average anchoring strength for a chest hair is 70 grams. That is, you can add 70 grams of weight to one chest hair before it breaks.
  • Beards of men contain between 7,000 and 15,000 hairs.
  • Men remove 8.4 meters of face stubble in their lifetime. It takes them approximately 3,400 hours to do so.
  • Because hair is so strong you could hang between 5,600kg and 8,400kg from one head of hair without it breaking (although your neck would not take it !).
  • As a rough quide, 20% of men in their 20s have pattern baldness, 30% in their 30s, 40% in their 40s, and 50% have pattern baldness in their 50s. If you get to age 60 without developing pattern baldness you will probably avoid it alltogether.
  • By age 50, 20% of women have thinning hair.
  • Our eyebrows contain 550 hairs, give or take a few.
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