and night sweats
can have several different causes and hope the CT scan of the paranasal sinuses
also covered the head and excluded intracranial pathologies.
function test would be an important test here.
The red plaques are probably unrelated to the headaches and night sweats in time, and if they are itchy red lesions slightly raised and disappear without a trace it means urticarial eruptions. Here too thyroid autoimmunity plays a role and therefore best to exclude with TPO antibodies
I do not knwo what subcutaneous tests your doctor is going to offer but cannot be more sensitive than skin prick tests.
Occasionally multople cardiac medications can cause the urticaria, so please check these out and discuss with your doctor.
80% of patients with urticaria do NOT have allergies.
Long acting antihistamines non-sedative are usually fine but in the elderly needs some caution as it causes dryness of mucosae.
Hope this helps.