So if heatiness ends up with kidney failure is the cause of death "heatiness" or "kidney failure"?
heatiness as derided as it as a non-scientific folk catchall term doesn't invalidate the fact that the patient / test subject is suffering some form of distress. Common folk parse the symptoms of general unease into this catchall.
Broadly and coarsely speaking, such distress as described in "heatiness" is likely to come from one of two sources. Disequilibrium in body functions and/or an Immunological attack on the body. Both vectors in MILD cases are typically helped by same said folk cures for "heatiness". Mild cold? hydration and vitamin c. dehydration? Hydration with "cooling" fluids. For all of medicine, most cures come from your own immune system if you look after it as I'm sure you're already well aware of. With sinkieland's chronic poor diet and little health literacy, solving "heatiness" in general does allow the body to function better in most MILD cases. Of course once the patient starts to have serious symptoms, off they run to the doctor. I would only dispel "heatiness" as a condition if patients refuse medical attention when their situation worsens.
So as stupid as it sounds. For the medically illiterate, "heatiness" and "heatiness" cures work most of the time to alleviate some of the distress for most of the things they encounter.
Let me try to put it another way. Speak the language that results in the best understanding from your listener. And if said listener is happy with his terms, and it works well enough. I'd rather not disabuse them of their familiarity. After all, I do expect when their "heatiness" cures don't work and the situation worsens, they will head off to professional help. Which they don't understand whichever way anyway.
Of course you probably feel differently...
something along the lines of "you twit!!"