Half a year ago I decided to do a somewhat homemade mercury provocation test(big mistake), aka I drank two tablespoons of chopped koriander with a glass of water in the evening and took a heavy metal urine test the following day.

Now, already half an hour after having drunken this nearly lethal coctail my face began turning all red, especially in the cheek area, my eyes became bloodbroken and itchy to a point where my subconscious mind just wanted to spoon them out. I was very miserable for a week after.

Next day the urine test showed a highly elevated mercury level, aswell as a medium cadmium one. So yes I definitivly think redness in the face can be related to mercury floating around in your system, or hugging your cells to death.