Demons have Heat Cycles, but Angels and humans don't -so in the House of Lamentation, Satan is the only one who goes into heat (as he's the only "true" demon in the family)

His heats only happen once a year or so, and normally he's able to handle it. His heats are aggravating and uncomfortable, but Satan has spent his entire life learning how to constantly keep control of himself. He could keep his heats contained easily enough, right? And he had... until the exchange program happened, and YOU came along.

He's the only one who has to go through the agony of Heat while sharing a home with you, and if he thought his heats were bad before? Oh, he had no idea.