Why do ponies get frizzy hair?

[CloudyGlow]

Some of the ponies I buy second hand have the frizziest hair.  How/why do they end up like that?

[Skeen]

Rough brushing by kids can stretch the nylon.  When it stretches it warps and kinks. 

Also some colors just have less quality than others.  Looking at you, green in Quackers's hair...

[ponycentric]

From what I've read and heard, it happens from a lot of brushing and handling.  Since the hair is a type of plastic it stretches and gets damaged when it's brushed a lot, making it look and feel frizzy.

[Baby Sugarberry]

Chemical damage can also cause or worsen frizz - bubble bath mixes for example, I'm fairly certain are a culprit since both my childhood seaponies had terrible frizz and they were rarely brushed at all.  Stretching, kinking and other physical damage are the usual causes.

[Leave a Whisper]

either by brushing too much, or not at all

[mlp4me]

What about all that pony nomming? They are a delicacy to some children...

[egyptiondragon]

What about all that pony nomming? They are a delicacy to some children...

This 

[lovesbabysquirmy]

Because their hair is plastic...

[hathorcat]

I will second the brushing. When you brush nylon hair you "pull" it and make it longer and then it contracts back into its original shorter form. Do that enough and you will break the surface as well as break down the hair. Ultimately that leads to damage and frizz.