Most people figure out their allergies pretty early on in life. You might be told about them as a child, and it’s usually only if you’ve never come across something before that you suddenly discover an allergy you didn’t know about.
So it’s a bit weird that this guy didn’t actually realize that he was allergic to something that he drinks regularly. How could he have thought that your entire face sweating is a normal reaction to drinking juice? I’m slightly worried about what else he might be eating that is bad for him.