answer:Anecdotally and indirectly, I’d say they do. I love DayQuil & NyQuil (“green-death fuckin’ flavor!”), but I seem to stay sick longer with it. I suspect it’s a combination of things. I only take it when I’m feeling really bad so already the sample is skewed to more serious ailments. They tend to curb my appetite so I eat and drink less and don’t get the same nutrition and fluid intake I would normally and need especially when sick. While I’m chugging the big-Q like cheap **** at a frat party I tend not to rest nearly as much as I should. Then of course there’s my inability to follow directions, so yeah I pretty much take a swig whenever I feel bad, which is well – constantly – so I’ve probably got some low-level acetaminophen poisoning going on. I suspect the combination of the above, are the real reasons relief meds make it last longer, not because they do anything directly, but rather the indirect effects keep us from doing what we’re supposed to. And as you said, your body is usually doing what it’s meant to do anyway so interfering with that as soon as one feels the first sniffle, particularly when only treating the symptoms, probably isn’t helping. Bottom line, under normal circumstances, let your body do it’s thing and use that stuff only when you need to improve your ability to sleep. The problem is a lot of times we use it so we don’t have to sleep, rest, and take it easy when we most need to – hence it takes longer to evict whatever cold/flu has taken up residence.