Hay fever sufferers often say they would do anything to stop sneezing.

But few would contemplate going as far as Professor David Pritchard.

In search of a cure for asthma, hay fever and other allergies, he let 50 hookworms burrow into his arm. They ate their way through his skin and, once in his bloodstream, made their way to his gut, where they began to reproduce.

Pritchard had a theory - that parasites could "cure" allergies and auto-immune diseases, including diabetes and Crohn's disease. He had noticed that in Papua New Guinea, and other countries where most people are infected with hookworms, there is a very low incidence of asthma and allergies.

This led him to wonder - could the hookworms be "distracting" or "dampening down" the immune system?

He hypothesised that, once in the gut, the worms secreted chemicals into the bloodstream which "turned off" the immune system, so it could not expel them from the body. He wanted to test his theory by infecting asthmatics in a clinical trial. But the Ethics Committee refused to grant him permission: they weren't confident that it was safe.

So, in that famous medical tradition, Pritchard infected himself, along with volunteers from his laboratory at Nottingham University. "My wife thought I was mad" he recalled.

He stuck 50 hookworms on a plaster and attached it to his arm. It began to itch - an excruciating pain, he says, far worse than a mosquito bite.

The worms - which grow up to a centimetre in length - spent two days in his skin before migrating into his blood vessels. Pritchard experienced no more symptoms until four weeks later, when the parasites arrived in his gut and began laying eggs. The eggs were excreted, but the parasites began sucking blood from his gut wall. He developed severe diarrhoea and began to ache under his ribs. Unable to sleep, he took de-worming tablets to get the bugs out of his system.

Was it worth it? What did his painful experiment prove, apart from that worms give you bellyache?

In fact, he had proved that the treatment was safe. Fifty worms? That was too many. But his colleagues who had taken 10 worms experienced no ill-effects.

Shortly afterwards, the Ethics Committee allowed Pritchard's team to begin a trial monitoring the effects of 10 worms on hay fever sufferers. They were infected in January, and now that we're in spring, when pollen counts begin to rise, the hope is that their traditional symptoms will be alleviated.

So, what if worm therapy is a success? Does this mean that soon we will all be lining up at the chemist to buy parasite patches and infect ourselves? Of course not. Pritchard is shrewd enough to recognise that hookworms are unlikely to be a big seller. Instead, his idea is to develop a synthetic version of the chemicals the worms secrete - one which would have the same effect on humans. This could be used to treat allergies by stopping the immune system over-reacting to pollen and dust mites.

One day, it might even tackle more severe auto-immune diseases such as MS and diabetes. This feat has already been achieved in animals by Professor Anne Cooke of Cambridge University. She took an extract from a parasite and gave it to a strain of mice with a genetic predisposition to diabetes; when injected, none of the mice developed the condition. Again, it is hoped that a similar drug could soon be developed for humans.

On Tuesday, Professor Cooke will address the Edinburgh International Science Festival alongside Pritchard, who will reveal all the gory details of his hookworm ordeal. It should be an engrossing tale - if not for the squeamish - and one that will offer hope for the many millions who suffer from painful, even life-threatening, allergies.