The answer: There is no evidence that using a nose spray will alter your test results.
TL; DR: The SARS CoV-2 rapid antigen tests (aka COVID-19 rapid tests) become positive if they find a lot of the protein that that comes from SARS CoV-2. It is not likely that allergy sprays would change the amount of virus in your nostrils or that its protein would not be detected. In theory a Neti pot or saline spray could do that, but it is unlikely.
🧪 Remember what the COVID-19 rapid tests detect? They look for an antigen (like the nucleocapsid protein) that is part of the 🦠 virus 🦠. When you have enough in your nostrils, your test will be positive. It is unlikely that any of the nose sprays mentioned would change the amount of virus in your nose. Using a Neti pot could wash out some of the stuff, including bacteria, viruses, and mucus but there would still likely be some viral protein around.
🚥 When you take a SARS CoV-2 Rapid Antigen test, the control line lights up regardless of what you put in. You put a drop of buffer into the testing unit. The buffer is a neutral solution that does not change when you add an acid or base to it. It is important because it makes sure that the test does not light up unless the SARS CoV-2 antigen is present. BUT, if you alter the buffer, you could get results that are either falsely positive or negative. In fact, there HAS been some talk of acidic substances interfering with test results. But this has to do with the testing mechanism itself and not with the sample from your nose (Read the study here.). So unless you are tampering with the buffer, omitting it, or adding it to your solution, you should not have unreliable results.
👃🏽 When you use an allergy spray, it is usually a corticosteroid (like Flonase) that decreases inflammation, thereby decreasing your allergic response. This will not have any impact on the presence or absence of the SARS CoV-2 antigen in your nose. However, when you use a Neti pot or saline spray, they are helping to keep your nasal passages from drying out and sometimes helping to unclog a nostril clogged with mucous. Theoretically this can wash out a little bit of the viral material, however it is very unlikely that it would do this to the extent that your test results would be altered (Note: If you use a Neti pot, make sure you do so safely. The FDA alert on this is linked below).
⚠️ If you are concerned about a specific nose spray that you are using, check the package insert for the test you are taking. 🧐 Many of the rapid test makers had the same question 🧐 that you did Beth! And so they 🔬 tested a lot of the common nose sprays like Saline and Fluticasone (Flonase). Here’s an example of the package insert for QuickVue (Scroll to page 12 and look for your spray.). Other package inserts list them too, so that is good news. Some of the manufacturers DO recommend that you wait 15-30 minutes after spraying before you take a test. We didn’t find good evidence for why this would be, but it is best to follow manufacturer instructions to ensure the most accurate results.
The bottom line: It is not likely that your nose spray will alter test results.
Stay safe. Stay sane.
Those Nerdy Girls