Warren's wife is stated on multiple occasions to be cheating on him. Lots of talk of infidelity.

A man shoots his wife, but it's revealed to be a blank.

A character takes a large dose of LSD for an experiment and we see his reactions to the drug for several minutes.

We see a prisoner screaming while being dragged to the electric chair. The execution isn't shown.

It's cheesy fun. The "Tingler" itself is clearly being held up by strings whenever it's on screen, so any potential horror is neutered.

Several scenes of The Tingler creeping up on and attacking people by gripping their throat or arm in its powerful mandibles. Screaming paralyzes The Tingler, and so attacks rarely result in serious injury.