Heartburn And Hives

Can gourmet mushrooms cause severe gastrointestinal reactions?

I added Alba Clamshell, Trumpet Royale & Forest Namedo mushrooms to a salad and within 30 minutes had severe gastrointestinal pain that lasted for over 4 hours. I slept but in the morning I still had residual heartburn, strange headache and flushing of face & neck with a hive itch feeling.

Are you sure about the safety of the mushrooms you added? The reason I ask is that part of your symptoms don’t match with food allergy. For example the gastro pain is not a typical symptom but red/flushed skin or hives is. Headache is not an allergy symptom but itching is.
Your reaction could be the result of a food intolerance which is medically different from a food allergy. Either way, you have to avoid the offending food.

Severe Allergic Reaction