When carbon dioxide (CO2) is blown through the sinuses in a kind of pressurized gas rinse, it may relieve symptoms like itchy, watery eyes, sneezing, and a runny nose, according to a new study. CO2 is a colorless, odorless gas that is exhaled with each breath. It also puts the "fizz" into soft drinks and is frozen to make dry ice.
And CO2 appears to work pretty quickly for allergy relief, says study researcher Thomas B. Casale, MD, chief of allergy and immunology at Creighton University in Omaha, Neb. "In this study it was within 30 minutes, and in a previous study we did it was within 10 to 20 minutes. So for patients that are having significant symptoms, it could provide very rapid relief."
Side effects were generally short-lived, but included headaches, tearing, and nose pain.
Casale, who has tried the treatment, says it feels like the sharp burn of a soda burp.
"It's almost like if you're drinking a carbonated beverage and somebody makes you laugh and it goes up your nose, and you know how it stings for a bit? Some people experience that with the carbon dioxide," he tells WebMD. "That sensation goes away as soon as you turn the gas off."
The study is published in the Annals of Allergy, Asthma, & Immunology. It was sponsored by Capnia, a company that hopes to market a handheld carbon dioxide device to treat allergies. Casale says he has no financial interest in the company.
Researchers aren't entirely sure how the treatment may work, but they have some theories.
One theory, Casale says, is that the gas probably helps to blow allergens out of the nasal passages, where they are causing irritation.
Rinsing the Nose With CO2
For the study, researchers recruited 348 adults who had been allergic to dust mites, cats, dogs, mold, or roaches for at least two years, as determined by a positive skin prick test and a need for medication to control their symptoms. They were asked to stop their normal medications before testing.
People in the study were randomly assigned to receive either carbon dioxide gas or a placebo. Those in the carbon dioxide group were further divided into groups who got either low or high doses of the gas for either 10 seconds or 30 seconds.
People in the treatment groups were asked to wear a nosepiece that was attached to a cylinder that was filled with compressed gas. A regulator controlled the flow of gas, so that study participants got either 5 milliliters or 10 milliliters of gas per second for either 10 seconds or 30 seconds in each nostril.
The placebo group wore the same device for either 10 seconds or 30 seconds with no gas flowing through it.
Study participants were advised that they might or might not feel the flow of the gas. Some participants in the placebo group reported feeling gas flowing through their noses, while some in the CO2 group said they couldn't feel anything.
All groups reported an improvement in their symptoms.
The placebo group reported that their nasal symptoms improved about 3 points, on average, on a 20-point scale.
The carbon dioxide groups reported that their symptoms improved by 3.7 to 4.7 points on a 20-point scale.
Only one treatment group reported relief that was significantly better from the placebo group, however. That was the treatment group that received 10 milliliters of CO2 per second for 10 seconds per nostril.
There was little change in nasal congestion.
More Research Needed
Experts say that despite its promise, carbon dioxide isn't yet ready for general use.
"The good news for patients is that there's ongoing research into new and novel ways to treat this chronic condition that affects a third of our adult population," says Stanley M. Fineman, MD, a practicing allergist in Atlanta. Fineman is also president-elect of the American College of Allergy, Asthma & Immunology.
"The nice thing about this potential treatment is that it is not a medication," he tells WebMD, "It's not a chemical."
Even if a CO2 treatment comes to market, the relief it offers is likely to be brief.
Fineman says it wouldn't replace disease-modifying treatments like allergy shots or longer term controllers like inhaled steroids.
"This would be more of a reliever for breakthrough symptoms," Casale says. "I think it could be equated maybe to how some people use over-the-counter antihistamines if they're having symptoms."