Ludoggy said:
Every restaurant you go to they keep ketchup out at room temperature.
And its *** vinegar and tomatoes. Bacteria doesnt grow well on acidy food.
Doesn't mean it doesn't grow at all. Bacteria lives in freaking volcanic vents at the bottom of the ocean where the temp is a constant 500+ degrees.
Personally, I just wouldn't take the chance. If it says "refrigerate after opening", I do it.