Red upper arms, intensified by temperature, no bumps

I have redness on my upper arms that is not sunburn and I'm not convinced it's keratosis pilaris, but haven't totally ruled that out. Tired of people looking shocked and commenting on my "sunburn". Although I am pale and this condition makes my arms look pink-hued, I still have a subtle olive tone and can tan. Curious to see if anyone knows what this is? There are no bumps, plugs, or roughness at all so I don't feel it's keratosis pilaris. Exfoliating my arms, as suggested for KP, would result in extra red and inflamed skin. Maybe it's rosacea? It does not hurt, but can feel hot to the touch sometimes. My face can get pink when I'm hot, but generally is not red or flushed.

There is always a slight flush on my upper arms, but it's definitely intensified by temperatures. The second I go in the sun, my arms start heating up and turning extra red. And I get the inevitable comments. I avoid sleeveless most days for this reason and have to mentally prepare myself for the comments if I choose to wear sleeveless. My arms get extra red, purple, and splotch-y in cold air-conditioned climates. The redness is concentrated a few inches past my shoulder and runs to the beginning of my forearms, but if I'm hot enough my forearms and hands will flush as well. Upper thighs and feet flush as well too, when I'm hot or exercising. Below is what my arms look like when it's "calm".

Thanks for reading! Any information or theories would be appreciated.