Comment by vbelenky

>This lamp would kill those friendly microbes.

Not really. Those microbes live deep in your pores where the UV wouldn't reach. Even if the UV totally scoured the surface of your skin, it would only be a temporary disruption, which we're generally ok with. After all lots of things disrupt the skin microbiome--showering, hand sanitizer (which DOES penetrate into the pores).

But I think UV skin microbiome disruption is likely to be pretty mild compared to things like eg hand sanitizer. Generally anything that lives on a surface (compared to liquid, and especially air) requires a much higher UV dose to inactivate, because even seemingly-smooth surfaces actually have lots of microscopic nooks and crannies for pathogens to hide in. And skin isn't smooth at all--it's got tons of visible wrinkles and surface complications and complicated geometry. Bacteria are also less sensitive to far-UV than viruses. So lamps that are dose calibrated to kill airborne viruses aren't going to have much of an effect on bacteria that live on a complex surface.

There's actually some data on this although sadly it never ended up published--my lab collected microbiome data for this 66 week hairless mouse skin exposure study https://pmc.ncbi.nlm.nih.gov/articles/PMC9691791/ and found basically no difference in microbiome between the exposed and unexposed mice. It didn't end up in the paper because nobody in the lab had enough bioinformatics expertise to do a nice publishable analysis and just had to take the bioinformatics centers' word on it that there weren't significant differences. Weak/hearsay-ish evidence but not nothing!

In-duct UV is a thing but it's really not ideal for preventing person-to-person disease transmission, for a number of reasons.