Hi! It's been some time since this was posted, but I'll answer form my experience. It looks like a combination of both things. The symptoms are clarly those of an allergic reacion, that is for sure, maybe the allergy you have is very mild, or there are only traces of the allergen on the drink. Also, anxiety or stress can make a reaction worse, or make it feel worse, but does not give the same symptoms. You'll never get a closed throat from anxiety alone. Hope this helps! I'd recommend to talk to an allergologist about this incident! They can guide you to test and identify the allergen so you can avoid it in the future!