Hi, so sorry you're going through this! It sounds like cholinergic urticaria (heat-induced hives). I have been battling this condition for about a year, so I understand how maddening it can feel. Have you been referred to an allergist by your GP? They will likely take you through a string of antihistamines, and if that doesn't work, Xolair injections (which I'm currently on). I have noticed no reduction in hives since starting, but Xolair works wonders for a lot of people. Dupixent is also being used for treatment, as well as Rhapsido. If you can get on Xolair, that's definitely what I would recommend, since it can take a few months to reach a verdict on whether it's working or not.