The way I understand it honey can go bad (breed bacteria) if it has been heated during processing. If you heat it too much, that is above 40 degrees celcius, then the antibacterial and curative properties are compromised and bacteria may grow.

So if you are wanting to keep some in your PSK I would make sure that it was raw (ununheated) honey from your local apiarist.

And don't leave it in a car on a hot day!