Q: Is adding temporary hair extensions to make a hair style, not permanent and the extensions are not real hair, permissible?
A: It appears in one Hadeeth of Bukhaari that Rasulullah (Sallallaahu Alayhi wa Sallam) cursed the female who adds human hair to her natural hair for purposes of beauty and make-up. Among the various reasons for prohibition is that human hair is sacred and cannot be used for any purpose once it has been severed from the body.
Thus it will not be permissible to sell and use human hair.
Using artificial hair (synthetic) and hair/wool from animals is permissible. (Raddul Muhtaar V19 P238). To sell it will also be permissible.
Allah Ta’aala knows best.
Moulana Yusuf Laher