The answer is very
easy. It is because of one of three things or a combination:
1) Lack of moisture in the
hair.
2) More impotantantly - Lack
of E.F.A.'s (essential fatty acids) (lipids)
3) Lack of protein
4) Long hair passed the neck
line
The cause for the frizz in
MOST cases are chemical services. It depletes the the hair of all the above.
Other causes my be poor diet , exposure to the sun or tanning beds, or
mechanical damage(irons-dryers).