Strange Reaction to Something so Innocent

The day started off happily.  My husband took our son to Starbucks and purchased him a bottle of Very Berry Naked Juice.  Sounds simple enough--apple juice, banana, strawberries, blackberries, and raspberries--AND natural flavor.  He's had all the fruits before without issue.  He's even had other types of Naked Juice like the Strawberry Banana.  But it was clear that this particular bottle didn't agree with him.  Within minutes of drinking it, my kid was panicking that his throat felt swollen and complaining that his heart was racing.  He dropped to the floor in agony and was gouging at his eyes, which had turned extremely red all around the outside.  Mind you this was 7 in the morning and I was hardly awake.  I flew out of bed to try to help him and get a handle as to what was going on.  I gave him a Benedryl and after a few minutes he calmed down and seemed ok.  I couldn't help but wonder if he had came into contact with peanuts while at the coffee shop.  We had a NAET appointment scheduled for 9 am, and I took the juice with us.  He was showing weak to the juice, especially in the lung area which is rare for him.  Wish I knew what this particular 'natural flavor' consists of, as my post from a year ago proves, it could be anything.