In an act of religious piety, hundreds of thousands of Indian women have their heads shaved, unaware that their valuable hair is then collected and used to support a multi-million-dollar fashion industry in the West.

It sounds like the ultimate story of exploitation. But is it?

Every day tens of thousands of Hindus make pilgrimages to the country's biggest temples.

They make special requests to the gods or give thanks for wishes granted. Many have no money to offer the gods; the most valuable thing they can give is their hair. The process is called tonsuring.

Indian women treasure their hair. They nurture and condition it, keeping it free of dyes and bleaches.

At the temples in southern India, dozens of barbers are lined up 24 hours a day, wetting their razors and shaving the heads of visiting pilgrims.

In the past in India, temple hair was used to stuff mattresses, but now, that has all changed.

When the hair extension industry kicked off in the Western world, temples found they could sell sacrificed hair to the middle men of the hair extension industry for $200 to $300 a kilogram.

The hair is then brushed and combed by hand at a factory in Bangalore, before being shipped to the Rome headquarters of the self-proclaimed founder of hair extensions, David A Gold.

By now its value has jumped to $500 a kilogram.

The colour is removed from the hair and it is dyed a range of fashion colours, before being sent to hair salons in more than 50 countries across the Western world.

Women pay as much as $4,000 dollars for a longer, thicker head of hair.

Win-win

The hair industry claims the situation is a win-win.

The Indian women are able to make a sacrifice to the gods, the temples make money, which they claim they use to support pilgrims and community programs, and the hair industry in the West has a new product to work with and happy customers.

But there are critics of the process. Jamelia, a British pop star and model, has used hair extensions, and at first was delighted at the look and the confidence they gave her.

But when a British documentary team took Jamelia to India to find the source of her hair, she became very concerned. Watching a small child being tonsured reduced her to tears.

Jamelia now says women seeking hair extensions should check that their "new" hair has been obtained ethically.

Lucrative trade

While the pilgrims might not feel exploited, there is no question that hair is now a valuable commodity, and the hair extension industry is making some people very rich.

Should those providing the vital ingredient also share the bounty?