A common allergy nasal spray may help lower the risk of contracting COVID-19, according to new research.

In a clinical trial of healthy adults, people who used azelastine nasal spray (Astepro, Astelin) regularly for nearly two months were significantly less likely to become infected with SARS-CoV-2 (the virus that causes COVID-19) compared to those who used a placebo.

The spray, widely available over-the-counter for allergic rhinitis (hay fever), also appeared to reduce some other respiratory infections, with only mild side effects reported. The findings were published online in JAMA Internal Medicine.

Researchers at Saarland University Hospital in Germany ran a phase 2, double-blind, placebo-controlled trial between March 2023 and July 2024. This means neither the participants nor the researchers knew who was getting the active spray and who was getting the placebo until after the study ended.

The study included 450 healthy volunteers aged 18 to 65. Almost all had been vaccinated against COVID-19 at least once, with a median of three doses, and none had signs of acute infection at the start. Recruitment was open to the public and promoted through universities, pharmacies, and social media. Participants were randomly assigned to one of two groups: one received azelastine 0.1% nasal spray, and the other received a placebo spray that looked and felt identical but did not contain the active medicine.

Both sprays contained common inactive ingredients such as hypromellose, sodium chloride, and purified water. The azelastine spray also had 1 mg/mL azelastine hydrochloride.

Participants used one puff in each nostril three times a day for 56 days. If they developed respiratory symptoms or had known exposure to COVID-19, they increased use to five times a day for three days. Testing was a central part of the trial. Participants took a rapid antigen test for SARS-CoV-2 twice weekly, done by trained study staff.

Positive results were confirmed with PCR testing. Those with symptoms but negative COVID rapid tests were screened with multiplex PCR for a wide range of respiratory viruses, including: rhinoviruses, influenza, respiratory syncytial virus (RSV), several coronaviruses.