The spray is derived from shrimp shells

The shells contain a substance called chitin.

By purifying chitin, it is possible to create harmless spores which trigger the immune system so it can fight hayfever and allergens like dust-mites.

Researchers from the University of Oxford hope it will be possible to develop a product that can be sold over-the-counter to allergy sufferers.

We would welcome anything that could relieve the symptoms for people with allergies without having any side effects Allergy UK spokeswoman

The lungs have evolved so that the immune system recognises and fights fungal spores because they can cause infections.

Fungal spores contain chitin, but they are not suitable as a basis for an allergy treatment because they could themselves trigger allergies.

However, shrimp shells also contain chitin, and scientists have found that purifying it creates micro-particles (CMP). CMP is the right size to trigger the immune system to produce cytokines which have a potent anti-allergy effect.

Researchers say a product based on shrimp-shell chitin should not trigger seafood allergies because it is based on a carbohydrate rather than a protein.

They claim the CMP spray has the potential to both reduce hayfever or allergy symptoms and even to prevent children developing allergies at all.

'Safe and gentle'

Studies in mice showed that those treated with a CMP nasal spray did not trigger allergies in animals that had been made sensitive to allergens such as house dust mites.

Medical Research Council scientist Dr Peter Strong, who is developing the CMP spray, said its advantage was that it was non-toxic, and was easy to produce because chitin is a readily available by-product of the fishing industry.

He told BBC News Online CMP could have many uses, such as helping the immune system fight off colds, but that its first use could be as a hayfever treatment.

"It's really interesting to have found a natural method, an immune stimulator, which could elicit a natural response in the body.

"This could be used to treat the signs of allergy and hayfever.

"And because it should be safe and gentle, it could even be used as a preventative medicine for children, to stop them developing allergies in the first place."

The treatment would do that by gently stimulating the immune system into a protective response to allergens rather than a defensive one.

Awards nomination

A spokeswoman for Allergy UK said it was important to find a way of treating hayfever and other allergies.

"It is an enormous problem. We know that 25% of all young people aged between 12 and 21 will suffer from hayfever.

"We would welcome anything that could relieve the symptoms for people with allergies without having any side effects."

Dr Strong now needs financial backing in order to develop the product.

He is one of around 30 nominees for the Medical Futures Innovation awards, to be given out at the end of October.