Human hair is increasingly being used in hair extensions

At a barbershop in New York, a beautician named Heavenly Cross slides a razor blade through a head of disembodied black hair. Sometimes her clients want to be Beyoncé, other times Rihanna, and sometimes they want the hair from "that Mary J. Blige video."

Across the globe, an Indian woman makes her way along the southern banks of the Sri Swami Pushkarini River in Andhra Pradesh, to the gilded temple of Tirupati. Once inside, a barber wets the woman's hair before weaving it into a braid. He places a band on either side of the braid, then slides a razor across her scalp.

Within hours, the hair that was an offering to the gods will be shipped to the port city of Chennai, where it will be auctioned to a Chinese export company. Once in China, the hair will be sorted, washed and packaged before being loaded into shipping containers bound for the shelves of discount beauty shops in the United States, where under names like "Bohemian Curl," "Hollywood Wave" and "Sea Breeze," Heavenly Cross will buy it and weave her clients into who they want to be.

So goes the global supply chain for human hair, a market that is growing at an astonishing rate of 40 percent annually.

Great Lengths Hair Extensions, one of the largest human hair venders in the industry, reports a 70 percent increase over the past five years. According to a report by the Professional Beauty Association, the past two years have seen a 28.5 percent rise in the number of U.S. salons that offer hair extensions.

The boom has been fueled by two major influences: celebrity culture and a wave of new technology for applying the extensions.

While American women once hid the fact that they outsourced their fuller hair styles, a new generation of female starlets — including Jessica Simpson, Brittany Spears and Fergie — openly admit to wearing other women's hair. Now the long-held celebrity secret of human hair extensions — in which tresses of imported locks are sewn, beaded or glued onto the follicles of hair beside the scalp — is out in the open.

The effect of the extensions is to increase fullness and length. Women with short or thin hair can suddenly have hairstyles they never dreamed of. The added hair looks healthy for an average of four months before it dries out from lack of nutrients, which are replenished when hair is growing.

Until recently, real human hair was too expensive for many women who wanted extensions. They had to settle for cheaper synthetic hair. In both cases, the hair was sewn together in tracks and then attached to the client's head. But a new technique called "strand application" has made extensions look better and last longer.

With strand application, small bits of keratin, a protein naturally found in healthy hair, are fused to the client's existing hair, several strands at a time. The extensions look and feel just like natural hair and stay in place for anywhere from four to six months before the hair dries out.

Upscale salons have long offered human hair processed in Europe, which is pricier. And those salons still charge a premium for extensions. Alexander Maud, stylist at Mizu Salon in Boston, says he charges from $2,500 to $4,000 for a full head of extensions.

But now less pricey salons are offering human extensions using the old weave technique with packages of human hair sourced from Asia, which are much cheaper. Discount beauty supply stores market full heads of "100% Indian Hair" for $60.

"We don't really know how all this hair is being taken," said Susie Smith, chief executive of Hollywood Hair Extensions, a salon and distribution company. "We have heard small bits and pieces about people being attacked for their hair or selling it to feed their families, but we're not really talking about it."

While there is a huge profit to be made on Indian locks, there is no monetary compensation for the Indian women who donate their hair to temples as an act of faith. Many women have no idea they are part of an expanding industry that crosses several international borders and is nearly impossible to regulate.

According to trade figures released by the United Nations, between 2009 and 2011, China tripled its imports of Indian hair, from 800 pounds a year to 2.4 million pounds.

Smith believes that if consumers knew where the hair was coming from, they would have second thoughts about purchasing extensions.

"I rarely get a client who asks, 'Whose hair am I wearing?' " Smith said. "They think about it like they are buying an expensive leather purse and not asking, 'What cow did it come from?' "