by FIONA MACRAE

Last updated at 19:04 14 September 2007

A bloodsucking tropical worm could hold the key to combating allergies, scientists believe.

Hook worms are thought to produce a substance that calms the overactive immune response behind our allergies.

They are already being tested on asthma patients, to see if they can ease their symptoms.

And in time the half-inch-long parasites could be used to treat a range of diseases linked to flaws in the immune system, such as diabetes and multiple sclerosis.

Today, the therapy is still in the trial stage - and is not for the squeamish.

Attached to the arm with a sticking plaster, the worms burrow through the skin and move via the bloodstream and lungs into the gut.

Here they latch on to the wall and produce the substance, which is thought to be their way of switching off the parts of the immune system designed to get rid of them.

The Nottingham University scientists were inspired by years of work showing that those infected by hook worms do not suffer allergies.

They tested the parasites, commonly found in Asia and Africa, on at least 25 volunteers in two trials.

The first trial, in which volunteers had up to 100 worms wriggle into their gut, determined that ten worms could be given without sideeffects such as diarrhoea.

The second, involving hayfever sufferers, showed that the creatures do not increase breathing problems as they travel through the lungs.

The findings offer hope to the millions-of Britons who develop an allergy in their lifetime, as well the two million diabetics and 85,000 multiple sclerosis sufferers.

Researcher David Pritchard told the British Association Festival of Science in York: "I am keen not to oversell because it is still very early but the message so far is good."

Successful trials could lead to allergy sufferers being given a dose of the worms every five years or so.

Hook worms usually make their way into our bodies through the soles of the feet. They do not multiply inside the body and can be removed using worming tablets.

Eventually, it may be possible to create a drug that alters the immune system in the same way.

Muriel Simmons, of charity Allergy UK, said the study held out "real hope", but warned that more allergy specialists are needed to ensure patients get the treatment they need.

Hook worms are not the only creepy- crawlies being tested as alternatives to modern medicine.

Recently scientists used maggots to clean sores contaminated with MRSA while leeches have been found to ease pain and inflammation for arthritis sufferers.