According to Webster’s Eleventh Collegiate Dictionary (2003), a superstition is “a belief or practice resulting from ignorance, fear of the unknown, or trust in magic or chance.”
Upon considering this definition, it is possible to see how a superstition and an obsession could be related to each other. Obsessions are often the result of the fear of the unknown, or a belief that things happen to you by chance more than they do to other people.
However, just because you have a superstition does not mean that you have OCD. In order to meet the diagnosis of OCD, a person must attempt to ignore or suppress the obsession or somehow neutralize it. Usually people with superstitions do not try to hide them; in fact, they are typically very vocal about them.
As a result of a superstition, a person may perform a ritual as a way to undo the effect of the superstition (such as saying “bless you” after a person sneezes in order to prevent their soul, which could be ejected from the body by a sneeze, from being taken by the devil).
However, this behavior does not meet the criteria for OCD because the ritual could be performed in many different ways, people vary their exact words, saying “bless you,” ” “blessings,” “god bless you,” and so on, and people often say the words quickly, almost without thinking and with very little fanfare.
A ritual is the exact opposite, it is typically exact and it often, but not always, involves several steps and can be quite prolonged.
It is possible that superstitious behavior could lead to OCD, but just because someone is superstitious does not mean that that person has, or will develop, OCD.