Facial flushing reaction after just one meal

Hi all, I’m trying to distinguish whether I have MCAS or not… I seem to have facial flushing, one hour after eating my lunch meal, almost daily now, eating the same meal. It lasts for 3-4 hours and is accompanied by other MCAS symptoms like diarrhea and stomach pains, brain fog, fatigue, for example. The weird thing is that when I eat some of these same food items at my dinner meal, I do not have the facial flushing. Furthermore, for two days I took Pepcid before the lunch meal and didn’t have facial flushing and then didn’t take Pepcid today before lunch and facial flushing was back. Could this be MCAS? Some of it adds up and then other parts of it don’t align with some of what you all share… looking for insight.