Hi definitelynotlistening , Your question about strep caught my interest. Fourty years ago the dermatologist I had at the time for plaque psoriasis, warned me about strep. I'm not any kind of medical professional and cannot vouch for the facts about the following words and advice. A close facsimile to his words: "With chronic plaque psoriasis you need to be extra cautious about sore throats. This (plaque psoriasis) is a disorder of the autoimmune system. Due to suppressed immunity, a sore throat could easily be strep. If strep throat is left untreated, the symptoms usually disappear but the disease is still present as an infection. It can cause serious problems including major psoriasis flares." And again, his words of advice, not mine, "If you have a sore throat, get a culture taken to rule out strep throat."
Over the years I have noticed whenever I have a cold or infection the psoriasis shifts into turbo mode. These days I have PsA which is in a different league but has similar problems.