The likely cause imo? Someone bought/used UVB fluorescent tubes/lights (~200nm) instead of LED UVA (~400nm) as blacklights. They're cheaper, brighter and have a stronger effect.
Unprotected skin/eyes can feel the difference in I don't think these were UVC, since the UV light affects DNA in a logarithmic scale. UVC is soooo much more likely to damage DNA, UVB is somewhat likely to damage DNA, UVC has a low likelihood of damaging DNA, blue light has an even lower chance of damaging DNA and so on. The time of exposure and effects were likely high nm UVB/low nm UVC. I could see this being the effects of a 280nm-315nm LED light source, or a skin treatment fluorescent tube. UVC bulbs and tubes are really hard to buy and cost a ton, so unlikely.
*I'm a nerd, wanted to solve myopia, there was a paper that suggested that UVB or UVA could help form crosslinked proteins that would prevent myopia from getting worse. It could explain why outdoor exposure helped so much. So I bought some of these UVB fluorescent bulbs and stared at them them for 10 minutes. Started feeling the itchy, burning feeling and stopped. Currently my theory of myopia has to do with regular defocusing to relax the eyes (that's what the myopia prevention glasses do)