Different people have different types of hair. While some have straight and silky hair, there are other who have wavy and curly hair. Hair should be stylized according to hair type. When you have curly hair, you need to look after it properly to stop it getting dry and frizzy. If you have the patience then you can blow dry it straight everyday, and/or use straightening irons on it, but if you do this then you have to take special care to keep your hair well conditioned and protect it from the heat.
