I just ate a slice of pepperoni pizza with parmesan cheese and red pepper flakes (I have eaten this exact thing many times before). Then after a couple bites I realized that it was becoming very painful to swallow. I tried drinking water but that was difficult to swallow as well. Most of my mouth and throat were burning but I wasn't in severe pain, I would say it was moderate discomfort. I went to the bathroom and a green film had formed on the back of my tongue. From what I could see, there was no discoloration to any other parts of my mouth. After about 30 minutes I no longer had any difficulty swallowing. I figure this must've been some type of allergic reaction, but I can't find anything about the green coating on my tongue. What could this be?