For the last month my Enzo (19 months/11lbs) has been suffering with horrible allergies

He's sneezing, eyes watering & just miserable. Around the same time I noticed a lump/sore on his left lower back. It looks like a crusty pimple, no liquid if that makes sense. He's been on a 10 day course of antibiotics to no avail, in fact the lump has gotten larger, and now bothers him.
He is scheduled for surgery on Monday. The vet will remove the lump & send it away to get tested. Tonight, while brushing him I felt at least 4 or 5 little bumps scattered on his body - I'm frightened