First of all thank you so much for helping your father with his medical condition and supporting him in his journey. My though, being a COPDer, things I have ran into that causes myself grieve at times. Is your dad hydrating (drinking) enough? Could this "heating" be from a reaction / side effect of one of his medications? What about the enviroment, yes as mentioned before allergies (they can change over time, yeah!). Is his home maybe over humid (to high of humidity)? These are some factors besides as already suggested from others that could be checked in to while waiting on the doctors appointments, just to try in help rule things out or finding the cause of his uneasiness of feeling heated. Sending hugs to you both, please keep us informed. Thank you