Over the years, curious British, American and Australian medical experts have come to observe and speculate. Some think the white ash smeared on the body, the juice squeezed from the yellow lime fruit or the milk poured on the pierced areas may help to numb the skin. But most admit they have no answer.

"The belief in Lord Murugan is what prevents the pain and the bleeding," says Krishna Vadyar, a priest at the temple which conducts the annual rituals.

There are plenty stories about what Thaipusam is about. Among the most popular is that it commemorates the day Lord Siva's consort, the powerful goddess Parvathi, gives her son, Murugan, the vel (lance) to vanquish three demons and their large army which were plaguing the world.

Thaipusam falls on a full moon day in the auspicious 10th Tamil month of Thai when the constellation of Pusam, the star of well-being, rises over the eastern horizon.

In Kuala Lumpur, the festival is celebrated on a mammoth scale at the Batu Caves temple on the outskirts of the city. It began in 1892, started by early Tamils who migrated to colonial Malaya.

Reportedly, two of them made the difficult trek up the ancient limestone hill and planted the `vel' in the cave. The cave, the size of a soccer field, houses a temple dedicated to Lord Murugan.

The vel, made of metal and shaped like a lance, symbolises Murugan who is also known as Velan.
 

On the eve of Thaipusam, a five-ton silver-chariot bearing Lord Murugan's image and followed by a procession of several thousand people leaves the Sri Mahamariaman temple in downtown Kuala Lumpur, on a 15-kilometre trek to Batu Caves. Drums beat out trance-inducing rhythms and long wooden pipes, known as nathaswaram, croon devotional tunes in a loud carnival atmosphere.

The ethnic Chinese in Penang and elsewhere in Malaysia also take part in the religious festivities
Hundreds break coconuts and offer fruits to the God all along the chariot's meandering route.

Throughout its history, the chariot has been pulled by up to six pairs of bulls. But in 2000, the organisers responded to accusations of animal abuse, by switching to a motorised vehicle.

However, in the island of Penang in northwestern Peninsular Malaysia, the chariot there continued to be pulled by the bulls. Many in the island's large ethnic-Chinese community also take part in the festivities, breaking hundreds of coconuts.

To many Thaipusam is the day of thanksgiving or atonement for wrongs.

Spectacular edifices or kavadis are often carried or pulled by the devotees with chains and ropes anchored in the skin of their backs or chests.

After ritual cleansing at a stream at the foothills, they walk up the 272 steps accompanied by family and friends.