I may have accidentally swallowed sheer white whitening strips during my sleep. the label says, "don't swallow the film" but nothing more. what is going to happen, and what should i do?

Probably nothing: The main component of whitening strips is hydrogen peroxide, and in high concentrations and in large amounts, it is poisonous to ingest. But you would have to drink a lot more than the tiny amount in the strips! Swallowing just 1 or 2 should not cause any problems except maybe a little indigestion. If you get severe upset stomach, though, get seen. And take a little Maalox or Tums (calcium carbonate) today.

Just watch for now.: It's doubtful that a one-time ingestion like this would cause you any harm. More harm might come in people who swallow them regularly rather than remove them and throw them out. But they're not supposed to stay on all night anyway.