The blessing of those who sneeze started when the great plague took hold of Europe. Sufferers would sneeze violently, a sign that they would soon die. As a result, The Pope passed a law requiring people to bless the sneezer
At the same time it was expected that anybody sneezing would cover their mouth with a cloth or their hand. This was obviously to stop the spreading of the disease but many believed that it was to keep the soul intact. Sneezing ‘into the air’ would allow the soul to escape and death would be imminent.
Until the plague struck things were very different. Those who sneezed were congratulated on expelling evil from their bodies.
Read more: http://www.dazeinfo.com/2010/06/22/superstitions-across-different-countries-an-overview/#ixzz3Ds0rwyKa