Have you tried antihistamines? H1/H2 blockers. I’ve had long covid for over a year and this with a low histamine diet has helped. Some people after getting COVID develop histamine intolerance or MCAS
People call me crazy for keeping a tube of horse paste on the ready for Covid. I tell them, I can't afford to lose my house over something as stupid as Covid. Not to downplay long Covid, but here in America, we don't have free health care.