It really depends on the type of hot sauce you have purchased. If the ingredients list vinegar and salt, then the vinegar inhibits the growth of bacteria. If the sauce is all natural and have for example, fruit with no vinegar or salt, then refrigeration is necessary. When we applied for our agricultural license to bottle sauces, the inspector suggested that we put refrigerate after opening on all our sauces, vinegar or not, to keep us from a problem with liability down the road. So, I'm not sure what the case is with the sauce you purchased, but if it says refrigerate, maybe you should play it safe and do so. It does not change the heat level if you don't leave it there for a long time and we also found it preserves the color. Judith Mad Pepper Co. http://market21.com/madpepco