Types of alternative hair

Alternative hair can be classified in two main categories: human hair and synthetic.

Synthetic

At present, wigs made from synthetic plastic fibers are the most common ones.
Synthetic wigs are indistinguishable from those made from human hair, even to the most trained eye, and have the advantage of a much smaller price tag; this allows to manufacture wigs with a much larger color palette, and a larger variety of models.
On the other hand, human hair is much more resilient.
Human hair wigs can be dyed or styled with heating appliances, a feat impossible to accomplish with synthetic hair.

Human hair

Most human hair used for wigs is derived from the continent of Asia (China, India, and to a very small degree, Southeastern Russia).
Europeans do not generally sell their hair, so called "European hair" usually comes from India or China.
There are different grades of hair.
The highest grade comes from young donors, and is gently processed in order not to damage the cuticles, this hair is called Remy.
Remy means that the hair's cuticles are facing the direction in which they grew, this is called unidirectional cuticle.
Cuticles protect the hair from damage and give the hair its natural look, they also prevent tangling.
Buyers must be very careful, the market is flooded with imitations, abusively called "human hair".
Lower-quality "human hair" extensions are often diluted with animal and synthetic hair to lower the price.
Yak hair can be curled, permed, relaxed, and colored but many people are allergic to yak hair.