Cause of extreme heat in the head and face?

Could be food allergies also a contributing factor.
Keep a food diary that coincides with the episodes.
Maybe she also itches in one place on her back after meals.
Have her liver checked.

Just guessing, just wondering, just trying to contribute ideas.

There is a type of dementia, "Lewy Body Dementia." One of its symptoms is the inability of the body to regulate temperature. It's part of the autonomic system of the body and a prominent feature of LBD.

Moongazer
Just keeping you company here, no real answer. Your mom’s redness is much worse than my mom’s. 
My mom’s face, especially her nose would turn red every once in awhile just out of nowhere. Once she was in the hospital and it did that. Doctors were not concerned. This didn’t happen often and we wondered if it was that she was under such scrutiny that we noticed it and it had always done so?
We let it go because anytime she bent over to retrieve something from the floor and the blood would rush to her head, her face would flush. Not like her nose that day but noticeable. Some people will flush bright red on their chest when nervous.
My moms face was not hot to the touch. Just red. Her brother does the same. Their skin was/is very fair and they both had/have abundant white hair so it really shows up.
Some people will do this when they are about to cry, you may have noticed, but again usually not as red.

I’ve been doing some reading on thyroid issues.
Sometimes younger women will think they are having menopause symptoms and it turns out to be thyroid problems. So I just now googled
will hypothyroidism cause hot red face and I got several hits. Seems they sometimes think it’s a skin disorder and treat it for that with no success and then find out it was their thyroid. 

So you might ask your mom’s doctors to check that. I know it’s routinely checked with blood work so may be easy to rule out.
Let us know if you find the cause.

You’re welcome, Moongazer. Hope she’s continuing to feel better. Meds are funny things. I recently was put on a new blood pressure Med. I took it at 7PM and my husband woke me, very worried, at 9PM. Doc had told me it also works for anxiety but she neglected to tell me it also has sedative properties!

Thank you all for your input to my inquiry! The heating of my mom's head was getting worse, so I called her Geriatric doc and she thinks it was the recent increase in Prozac from 20 mg to 30 mg. Doc reduced her Prozac down to 20 mg and so far my mother's symptoms have subsided. We don't know if there is a direct correlation or just a coincidence, so waiting and watching.

I agree call the doctor. It could be blood pressure issues and it does sound like menopause symptoms. You might want to check w/ the pharmasist to see if she is on any drugs that could cause this or any combo. I used to flush when i wasnt taking hypertension meds or my bp was up ..esp if i had even a sip of alchol

Could be something simple or more complex. Drinking coffee can even make me feel warm, as can mood changes, and those kind are rapid and drastic. Although it doesn't happen that often, anxiety is another factor. I used to have it when I was in school, starting a mid-term and momentarily drawing a complete blank. Now it's when I become overwhelmed at all the post-death work I have to do, all the deadlines, trying to balance care of 2 houses, etc.

But I'd see her internist for a thorough check and blood work.

And, to add to Holiday’s answer, this is something you need to at least call her doctor about. Even if we were medical professionals on this site, there’s no way we could or should offer a diagnoses or suggest treatment. Call her doctor tomorrow and report her symptoms and see what they say.

Spiking a fever can make the person’s face and neck feel hot to the touch.

Also, menopausal symptoms make the face feel hot. Other hormonal problems could possibly cause a hot feeling to the face, such as thyroid problems.

Medication can cause hot flashes too. So no other symptoms along with the hot feelings on the face and neck?

This is the kind of mystery symptom that most doctors hate to deal with.