However there are some people who develop hypochondriac conditions and are "relieved" of these symptoms through the psychosomatic effect of placebos. This should not be confused with superstitious beliefs as it confers a psychological fault to their health.
It is not a full out "no" because the superstition got started by an observed occurrence. Such as "when a black cat crosses your path, bad luck will follow" And it probably did in one case (but in reality, not because of the cat) Just circumstances were such that bad luck did follow (no matter what). But unless it can be repeatedly shown that that is the case a single occurrence does not make it a truth.
As for ailments, we are all different and our intensity of ailments vary and our individual reaction to chemicals also vary. So what works for one person, does not necessarily work for everybody.
Generally speaking many ailments are over within a week to 2 weeks. This is why you often hear the doctor say "take 2 aspirin and call me in a week" Most likely you are on the upswing from the disease by then because your bodies natural defense system has multiplied enough to combat the infection..