Hundreds of thousands of asthma sufferers have flocked to the Indian city of Hyderabad convinced that eating a medicine of live fish and special herbs will cure them.
The wriggling live fish "helps clear the throat of phlegm"
The southern city's Goud family has been dispensing the medicine at this time of year for nearly 50 years.
They say they received the formula from a Hindu saint.
Sceptical scientists say the formula should be revealed for scrutiny but the family says it fears others will then exploit it.
The time of the treatment is fixed each year by astrologers and normally coincides with the arrival of monsoon rains.
If all the instructions are carefully followed we can
guarantee a 100 per cent cure
This year it began on Sunday night outside the Goud family home even though the monsoons have been delayed.
Patients must swallow the live fish - a murrel or sardine - along with a ball of mystery yellowish paste, then go on a strict 45-day diet of 25 different foods, including lamb, rice, sugar, dried mango, spinach and clarified butter.
"If all these instructions are carefully followed we can
guarantee a 100% cure for any patient no matter how bad their asthma," says family patriarch Harinath Goud.
Up to half a million asthma sufferers are expected to take a
dose - administered free of charge - in the next few days.
Special trains and buses are laid on from across India to bring believers to Hyderabad. Some patients travel from overseas.
There is absolutely no clinical evidence to prove it works
Dr Sumanth Mantri, chest specialist
Baldev Singh has travelled from the north-western state of Rajasthan for a fifth straight year.
"I am told that one should take this medicine for at least seven years to root out the problem of asthma completely," he said.
Preeta Mandlekar, 27 and from Bombay (also known as Mumbai), said: "The first time I had to do it I was terrified by the idea of having to swallow a live fish. But now it's not a problem; it just slips down the throat and disappears in a flash."
The Gouds say the wriggling fish helps clear the accumulated phlegm in the throat.
However, doctors have urged the family to disclose the formula.
"If they refuse to do so, the government should withdraw
its support for the event," said MV Ranga Redy of the
Indian Medical Association.
Dr Sumanth Mantri, a chest specialist at Hyderabad's Apollo Hospital, said: "There is absolutely no clinical evidence to prove it works... this acts more as a psychological than a clinical cure. There can be some temporary relief."
The People's Awareness Forum, a group that tries to
dissuade people from following rituals, says it will take
the family to court if they continue to refuse disclosure.
But Bathini Harinath Goud, one of five brothers who make the yellow paste, said the remedy would lose its potency if commercialised.
"We will continue the distribution of the medicine until
the last man gets it," he said.
Nearly 200 family members and volunteers are administering
the fish and about 5,000 police officers are controlling the crowds.