In a nutshell, we showed that over-the-counter cheap generic antibiotic neomycin can be repurposed in nasal formulation to prevent & treat infection, block transmission, and reduce disease burden against a wide array of viruses. Since this is a host-directed strategy and virus-agnostic, it holds promise as a prophylactic strategy against any viral threat.
The advice in the screencapped thread was to apply a little with a q-tip to the inside of the nostrils.
There is no info on any dangers of doing this very often, but if you can't avoid a high-risk environment it's worth trying.
Here's a thread about the study. https://threadreaderapp.com/thread/1782535781338222960.html
here's the study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5918160/
It's not being used to treat a bacterial infection in this case, whatever properties it has causes the immune system in the nose to go into virus-attacking mode. So I would think the of overuse is minimal.
Probably not best to use it daily, but for occasional high risk situations it shouldn't be a problem.
Prophylactic use of antibiotics is still use of antibiotics, even if it's being used for stimulation of toll like receptors. The bacteria don't care if you're trying to kill them or not. Benign organisms can still develop resistance to an agent and pass it off to hostile ones.
Now, resistance to this particular agent is not uncommon, so it's not catastrophically harmful to use it for that purpose. Other antibiotics see use for purposes other than killing or suppressing the growth of bacteria as well (erythromycin for gastric motility, for example). I'm curious about the actual degree of benefit this measure confers in a human sample population, and am generally not a fan of putting petrolatum-based products where I can inhale them as I'm paranoid about accidentally giving myself lipoid pneumonia.
It doesn't sound like you need to coat the inside of your nose, just put enough to trigger an immune reaction, so I would guess occasional use wouldn't destroy your nasal biome. Plain neomycin without the petroleum jelly should work the same, if you want to avoid petroleum jelly.
This needs more study to measure exactly how effective it is, but the one of the researchers doing the study, Prof Akiko Iwasaki, is a highly regarded immunobiologist.