Why honey doesn’t spoil

• Acidity. Most bacteria prefer neutral growing conditions. The enzymes bees use to break down the sugar in nectar make it more acidic and less appealing for bacterial growth.
• Sugar content. Honey has a lot of sugar, but only 18% water, which is not sufficient for most bacteria to grow. Honey has so much sugar that it's hygroscopic - which is the ability to absorb moisture out of the air. When honey is exposed to humidity, more water is added, and when the water content rises above 25%, bacteria will eventually be able to grow. That is why the container of honey should be closed.
• Antimicrobial compounds. Hydrogen peroxide is produced as a byproduct of some of the enzymes used by bees to digest more complex sugars. Some honey types also contain antimicrobial compounds such as defensin-1, an antibiotic produced by bees.

Combined, these three properties mean honey is very stable as long as it's not exposed to outside moisture or humidity.