Portabella mushrooms or hummus Within 3 hours of eating portobello mushrooms I began to feel a strong wave of nausea. Within 20 minutes of feeling nauseous there was an unsuppressable urge to vomit. I vomited 3 or 4 times throughout the night and again in the morning. I also have extreme diarrhea. 2 days later and I still feel dizzy and mild nausea when I eat.