Basic facts
Called khite in Arabic and fatlah in Egyptian, it’s a less common method in the West for removing hair at the root, used primarily on facial hair. Rows of stray hairs are yanked out with twists of cotton thread.
Description: The practitioner holds one end of the cotton thread in his or her teeth and the other in the left hand. The middle is looped through the index and middle fingers of the right hand. The practitioner then uses the loop to trap a series of unwanted hairs and pull them from the skin. There are also devices made that can hold the thread during the procedure.
Advantages: Inexpensive, fast, neat, considered less painful than plucking for many. Good for eyebrows and facial hair. Like plucking, results can last up to two to four weeks.
Disadvantages: Hard to find a professional practitioner outside large cities. Can be painful and cause itching afterwards. Side effects can include folliculitis, a bacterial infection in the hair follicles, skin reddening or puffiness, and changes in skin pigment.
Clinical data:
Chicago Tribune staff reporter Quynh-Giang Tran wrote a nice 
article “Ancient technique raising– and shaping–area eyebrows”
Costs:
$5 per treatment for eyebrows; more for larger areas
Background facts
Marketing terms and tactics:
Historical overview:
The history of threading is not clear, with some claiming it began in Turkey. threading hair is so basic to women in the Middle East and India that it can be compared to girls learning to braid each other’s hair as children. Traditionally, threading is used on the entire face, including upper lip, chin, eyebrows, sideburns and cheeks. Here in Chicago, salons performing it can be found in the Indian and Muslim neighborhoods. Most American cosmetologists are not trained in the procedure.
Government regulation:
Many states require a cosmetologist or aesthetician’s license to do hair removal like threading.