Hidden abilities
Sam wasn't the only Winchester with an unusual power. Teeny tiny 8.15 Spoiler
Dean never had it in him to tell his brother that he wasn't the only freak in the family, the only one with an ability. He didn't even know if he had always had it or if he got blindsided by some curse some day and nobody realized it, but he became aware of his own ability as a child.
Not that it was that useful, he would have preferred something more cooler. In comparison to Sam he was still a lot better off.
Dean sneezed and felt his throat constrict. Great, for that reaction through a closed door there had to be a lot of them there. Sam opened the door and they saw the reason for Dean's allergy attack: the victim had been a crazy cat lady. At least a dozen of them watched the human newcomers suspiciously. It would only be a matter of time till somebody remembered Ms Perry' s cats. In the experience of the Winchesters people were better to animals then their fellow humans. They would be cared for.
Another sneeze and Sam looked to his brother. "You Okay? You want to stay outside while I look for anything that could be a motive to kill her?"
Dean swallowed against the feeling in his throat and ignored the tickling in his nose. "It's alright. You go up and search there. I stay here. I go out if it gets to bad." Sam nodded and went up the stairs.
Dean waited till he was sure his brother couldn't hear him anymore. Sometimes his ability did have its uses. He focused his attention on the cats. "Can one of you tell me why your human was killed?" Perhaps one of the little fleabags had witnessed the whole thing.