If you were alive in London in the mid-1600s, you wouldn't have known what was causing the Great Plague, which wiped out 100,000 residents, almost one-fourth of the city's population. You wouldn't have known that the bacterium Yersinia pestis was responsible, or that it was spread by infected fleas. Like many, you might have believed that something bad was in that murderous air -- something that you hoped could be defeated by tobacco smoke.
One of the many myths circulating at the time encouraged people to smoke in order to stay healthy. At Eton College, smoking became a requirement, and violators were punished severely if they were caught not smoking. Other methods to fight the supposedly foul air: burning "sulfurous brimstone" (the recommendation of the College of Physicians), wearing perfume, and surrounding yourself with fragrant flowers.
Other potential cures for the Great Plague:
Spanked for not smoking... Any excuse.