Haven't heard about COVID tongue before, but the shingles+flu combo I caught this past fall left me with dermatographic hives that only just stopped around 3 weeks ago. Would randomly come up, usually across arms, hands, chest, neck, face and all over my scalp. Itched and burned like hell and if I scratched anything, would leave raised welts all over my skin. Have never had that before and it went on for at least two months.
I didn't test for Covid, so have no idea what it was. I wouldn't have treated it any differently from a regular flu (IVR+HCQ I got from a compounding pharmacy, plus the usual supplements), so didn't see the need to test.