London: Scientists claim to have discovered a new, potentially safer way to tackle your sneezing fits - squirting carbon dioxide into the nose.
A clinical trial showed that patients experienced relief from symptoms such as sneezing, congestion, itching and watery eyes within 30 minutes, and the effects lasted for an average of four hours.
The researchers said their new treatment, which uses a hand-held device to fire a ten-second burst of gas into the nostrils, could be a faster-acting and potentially safer alternative to current steroid-based nasal sprays.
Millions of people around the world suffer from allergic rhinitis, or year-round allergies. The symptoms vary from a runny nose and itchy eyes to severe asthma.
For the recent trial, researchers at Creighton University in Nebraska, US, recruited 348 adults with year-round nasal allergies. Half were given the CO2 treatment, while the rest a dummy device that didn't squirt anything into the nose.
The active treatment patients were further split into four; these were given a low dose of the gas for ten seconds, or a high dose for ten seconds, or a low dose for 30 seconds or a high dose for 30 seconds.
The results, published in the Annals of Allergy, Asthma And Immunology, showed that after 30 minutes the carbon dioxide groups reported less congestion, itching, sneezing and watery eyes.
The benefits of the spray - developed by US firm Capnia Inc - lasted for up to six hours, the researchers said.
In a separate study, researchers at the University of Chicago gave 12 allergy sufferers a 20-second burst of carbon dioxide and then exposed them to ragweed pollen, an allergen found in the US.
They found the carbon dioxide volunteers suffered a much less severe allergic reaction than a group not given the gas. It's not clear how the gas works on allergies, but past research has suggested it may block the release of a chemical called calcitonin gene-related peptide that is thought to be involved in triggering nasal allergy symptoms, the researchers said.
Dr Bill Frankland, from the London Allergy Clinic, said that although the treatment appears to work quickly, it does not provide the long-term relief patients get from steroid sprays, which last up to 24 hours.
"It might be useful as a quick fix," he said.
The researchers also said the treatment is not entirely benign - inhaling large quantities has been shown to cause hypercapnia, a condition where there is an increased heart rate, blood pressure, headaches and drowsiness.
The device to squirt the gas is still being developed, but if trials are successful it could be available within five years, the researchers said.