Well the vinegar in the ketchup counteracts with the tomato sauce and activates rarely used sweat glands in the temple region. The sweat glands have so much stored sweat it releases at a quick pace. On rare occasions it gets so backed up it comes out in spurts. Often causing the person next to you much discomfort. This condition is rare and often deadly. If I were you I would go see a doctor immediately. Good luck and let the force be with you.
