Common Allergy Spray Cuts Covid Infections By Two-Thirds

Twice-weekly swabs, three daily sprays, and a surprise: fewer infections.

In a randomized, placebo-controlled trial at Saarland University Hospital in Germany, a decades-old antihistamine nasal spray, azelastine 0.1 percent, was linked to a roughly two-thirds reduction in PCR-confirmed SARS-CoV-2 infections over 56 days. The phase 2 study, published September 2 in JAMA Internal Medicine, enrolled 450 healthy adults and tracked both SARS-CoV-2 and other respiratory pathogens under close, real-world conditions.

The numbers land with uncommon clarity. In the intention-to-treat analysis, 2.2 percent of participants using azelastine tested positive for SARS-CoV-2 by PCR, compared with 6.7 percent on placebo (odds ratio 0.31, 95% CI 0.11 to 0.87). Symptomatic Covid infections fell too, 1.8 percent vs 6.3 percent. Time to infection lengthened by about 12 days among those who did get sick, and self-reported illness days were lower overall. Even rhinovirus, a notorious spoiler of winter schedules, showed up less often in the azelastine group, 1.8 percent vs 6.3 percent.

“This clinical trial is the first to demonstrate a protective effect in a real-world setting,” said Professor Robert Bals.

It is a tidy outcome for a simple habit, one puff per nostril, three times a day. And it is not happening in a vacuum. Vaccination and widespread immunity have reshaped Covid risk, but preexposure options remain thin, especially for high-risk people and during variant waves. Monoclonal antibodies that once worked lost ground as the virus evolved. A new preventive antibody exists for the immunocompromised, but its potency has waned against recent Omicron sublineages. A readily available spray that reduces infections would not replace vaccines or masks, but it could add a layer that is pragmatic, cheap, and easy to keep up with. That matters for workplaces, schools, airports, and anyone doing the mental math before a crowded event.

There is, of course, the buried lede. The study was sponsored and the investigational product manufactured by URSAPHARM Arzneimittel GmbH, a Saarbrücken-based company that sells azelastine. Several authors reported relationships with the sponsor. The researchers followed Good Clinical Practice, preregistered the trial, and kept investigators blinded. Still, readers should note the commercial stake. My take: the data look promising, the conflicts are disclosed, and replication by independent groups will decide how durable this signal is.

Safety tracked with expectations. Adverse events were similar between groups, with a higher share of known azelastine annoyances such as bitter taste and occasional nosebleeds. Serious adverse events were rare and not considered treatment-related. Compliance was supported by frequent on-site rapid antigen testing, with PCR confirmation for positives, and multiplex PCR for symptomatic negatives to catch other viruses. The regimen also allowed short bursts of five-times-daily use during high-risk exposures, a detail that will interest travelers and healthcare workers.

Why might an allergy spray blunt viral spread? Azelastine is more than a histamine blocker. In vitro, it shows antiviral effects against SARS-CoV-2 and other respiratory viruses, with proposed mechanisms that include interactions with ACE2, inhibition of SARS-CoV-2 Mpro, sigma-1 receptor modulation, and ICAM-1 effects relevant to rhinovirus. The nasal epithelium is the front door for many pathogens. Keep that entryway hostile to viruses and, turns out, fewer invited guests make it inside.

“Azelastine nasal spray could provide an additional easily accessible prophylactic to complement existing protective measures, especially for vulnerable groups, during periods of high infection rates, or before travelling,” Professor Bals explained.

Limitations deserve daylight. This was a single-center study in a mostly young, vaccinated, and White cohort, with low overall event counts. Sensitivity analyses showed that statistical significance was lost under some missing-data assumptions, though none favored placebo. Bitter taste may have unblinded some participants. And the placebo formula, which included a viscous polymer, might itself offer a mild barrier effect. All reasons to treat the two-thirds figure as a credible estimate, not a guarantee.

And yet, the practical appeal is hard to ignore. An over-the-counter product, modest side effects, and measurable benefits across multiple endpoints. If larger multicenter trials reproduce these results, expect a small commercial scramble and some public-health recalibration. A spray on the way out the door, like keys and wallet. As habits go, that one is easy.

Journal: JAMA Internal Medicine

DOI: 10.1001/jamainternmed.2025.4283