system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What about honey makes it not expire?
gpt
The main reason is because honey is almost completely sugar. That high sugar concentration dehydrates any cells that try to take up residence through osmosis. (Osmosis being like a gravitational pull toward balance.) If there's water inside of a cell that falls into the honey, the honey will pull water out of the cell until the proportion of water to sugar inside the cell is equal to the proportion outside the cell.

Since the honey had such a high sugar content, a single cell just doesn't have enough water in it to make a dent in that so the honey ends up pulling nearly all the water out of the cell, killing it in the process.

There are some things that can survive without any water; botulism spores have already been brought up and are a great example of why we pasteurise honey, despite how well it kills bacteria on its own.

There are other properties that play lesser roles like a chemical secreted by the bees called defensin-1 which works as an antibiotic but these other properties pale in comparison to the mighty osmotic pressure.

What this means, though, is that, yes, honey has antimicrobial properties but the main one (osmosis) goes away the moment you dilute it because the balance mentioned earlier is much easier to reach if the overall solution has a lower percentage of sugar.

In turn, that means that honey does not pass it's abilities on to you by drinking it since you dilute it with your saliva and stomach acid. In other words, if someone tells you it will help fight off a cold because of its antimicrobial properties, they don't know what they're talking about.

It will, however, make your throat feel better temporarily but that's another ELI5.