There has been a global increase in the prevalence of allergies and auto-immune diseases, particularly in developed countries.

One theory is that such illnesses could be the unintended consequence of modern hygiene in preventing childhood infection.

Now a new Australian study has lent some credence to that hypothesis.

Researchers at Brisbane's Princess Alexandra Hospital have shown for the first time that parasitic hookworms could hold the key to treating coeliac disease, which is caused by gluten intolerance.

The scientists recruited 20 participants for their human trial through the Coeliac Society.

They infected half of them with live human hookworms. The parasites burrowed into participants' skin and entered the bloodstream after being applied to the forearm.

They then travelled via the lungs to the gut where they happily colonised.

For 21 weeks, the coeliac patients were fed white bread each day and were examined for a reaction.

The study's co-author, Dr James Daveson, says patients with the parasitic gut worm fared dramatically better to gluten exposure than those without.

"They experienced less inflammation and less damage was seen in the intestinal wall," he said.

At the end of the trial, the volunteers were offered worm medication to rid themselves of the parasites, but all chose to keep their worms.

The study will be presented at the Australian Gastroenterology Week conference in Sydney.

The researchers say further trials are needed, but they believe the findings could help in the treatment of other auto-immune diseases including Crohn's disease and multiple sclerosis.

Dr Daveson says people need parasites for optimum health.

"Over the last two to three generations we've got cleaner and lived in more hygienic surrounds and we've effectively de-wormed ourselves," he said.

"But parasites have been in our bowels for millions of years and we think they probably should be.

"Without them, one arm of our immune system gets up-regulated too much - it becomes too strong - and by introducing these parasites, downplays that arm of the immune system and brings out the other arm back into equilibrium."

But Dr Daveson cautions against rushing out to try and catch hookworms.

"The best treatment for coeliac disease remains a strict gluten-free diet," he said.

"We're commencing the next phase of this trial this month, but until further work is done and things are clearer, patients should remain on that diet."