What
is the maximum length that hair can grow to
If you do not cut your hair then you can grow it quite long, but
there is an upper limit to the maximum length that you can grow
your scalp hair.
We need to draw on three aspects of hair biology research to
define the maximum length that scalp can grow to. There are various
papers
that examine the time duration for scalp hair follicles are actively
producing a hair fiber. The most frequently quoted time period
is
1000 days, but this figure is only a rough approximation. The
time duration of anagen growth, plus knowing what length of hair
fiber
a scalp
hair follicle can produce per day, will enable a calculation of
the average maximum length that scalp hair can grow to. Perhaps
to complete the calculation you may need to know the density of
hair follicles on the scalp.
Research on humans suggest that active hair fiber growth production
from scalp hair follicles may last anywhere from 500 to 1800
days. In normal
haired individuals about 80% (min. 70%, max. 90%) of hair follicles
are in a growth phase with the remaining 20% in a regression or
resting
phase.
Hair follicle
density on the scalp is 200-300/cm square, that is about 100,000
to 150,000 hairs total. The scalp hair fiber growth rate is between
0.3 to 0.35mm a day. For the most part, the studies were done
with male volunteers, but a few other studies indicate similar
results
for women too.
If you put it all together in a calculation, the research
would suggest that the maximum length scalp hair can grow to is
between 20 and 60 centimeters and the sum total length of hair produced
each year is about 9km! However, from the picture below you can
see that some people are able to grow their hair much longer. The
upper limit to scalp hair length is determined by our genes. Some
people have genes for short hair, others grow hair much longer.
What
is the maximum length that hair can grow to references
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M, Loussouarn G, Hourseau C, Grollier JF. Ageing and hair cycles.
Br J Dermatol. 1995 Jan;132(1):86-93.
- Courtois
M, Loussouarn G, Hourseau S, Grollier JF. Periodicity in the growth
and shedding of hair. Br J Dermatol. 1996 Jan;134(1):47-54.
- Saitoh M, Uzuka M, Sakamoto M. Human hair
cycle. J Invest Dermatol. 1970 Jan;54(1):65-81.
- Braun-Falco O. [Dynamics of normal and
pathological hair growth]. Arch Klin Exp Dermatol. 1966;227(1):419-52.
- Barman JM, Astore I, Pecoraro V. The normal
trichogram of the adult. J Invest Dermatol. 1965;44:233-43.
- Myers RJ, Hamilton JB. Regeneration and
rate of growth of hair in man. Ann NY Acad Dermatol 1951; 53:
562-8.
- Trotter M. The life cycles of hair in selected
regions of the body. Am J Phys Anthrop. 1924;7:427-37.
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