Garrick smiled at the Professor... seems she recognized him after all. Mhm. Raising his hand he said, "Well they both have to do with fear, don't they? While the boggart turns into what one fears the most the Dementor kind of... makes you feel nothing but fear of sorts. I mean, you feel no happiness during a Dementor attack." Or something to that effect.

And WHY were they all sneezing? Just to be on the safe side Garrick pulled his shirt up over his nose and mouth. They could all be contagious and spreading their disgusting germs at the moment. ICK!