This is based on a misunderstanding. Loss of quality happens only during the compression that is done when an image is saved as JPEG. But it doesn't matter whether it was edited or not.

So: you will (with some very specific exceptions, see comments) lose quality if you open an image in an image editor and re-save it, even if you didn't make any edits. But if you only open it to display it and then close it instead of saving, then nothing will change.

By the way: this is only for traditional image editing programs like Photoshop. Programs like Lightroom that "develop" RAW files follow a different approach (even when handling JPEG files): they always keep the original image intact and separately save the editing steps that were done, which are applied when exporting the final results. So with such programs, you don't have to worry about losing quality (more than once, that is). But then, you shouldn't be using JPEG source files for them anyway.