Why does honey hardly ever spoil?

KohakuA jar of honey seems perfectly fine even after sitting on the shelf for ages. Why is that?

The answer in 30 seconds

I have summed up its secret to lasting so long in 30 seconds.

Honey rarely spoils because several things work together: it has very little water and a lot of sugar, it is strongly acidic, and an enzyme added by honeybees produces hydrogen peroxide. Because of this, bacteria and mold can hardly grow in it. However, if you leave the lid open and it absorbs moisture, it can go bad.

A wooden honey dipper and a piece of honeycomb filled with honey — Comb honey cut straight from the hive, with a honey dipper. Inside the small cells of the comb, the bees dry out the water from the nectar.Photo: Shixart1985 / CC BY 2.0 (cropped) / Wikimedia Commons

Little water, lots of sugar

Flower nectar is a runny liquid that is 60–80% water. Honeybees carry it to the hive and fan it with their wings to dry out the water, turning it into a very thick sugar liquid. In a liquid with that much sugar, water is pulled out of the bodies of bacteria, so most microbes cannot grow.

Strongly acidic

Honey is an acidic food with a pH of about 3–4.5. Many bacteria have a hard time growing in such a sour environment.

A disinfectant made by a bee enzyme

Honeybees add an enzyme called glucose oxidase to the nectar. This enzyme turns part of the sugar into gluconic acid and hydrogen peroxide. Hydrogen peroxide is a substance that kills microbes, and it is also used as a disinfectant. Researchers explain that this enzyme keeps the nectar from spoiling until the sugar becomes thick enough.

Figure: 3 things that protect honey

KohakuSo the bees' own enzyme makes a little disinfectant. How clever.

It can still spoil

There are even stories of honey thousands of years old being found unspoiled in Egyptian ruins. However, honey easily absorbs moisture from the air. Experts warn that if you leave the lid open and the water content rises, it can spoil. When you store honey, it is important to close the lid tightly.

Want to know more?

Never give honey to babies under 1 year old. It can cause infant botulism, and the bacteria behind it are not killed by normal cooking.
Molasses, another sugary syrup, has a pH of about 5.5, so it is less acidic than honey, and even though it keeps a long time, it eventually spoils. Honey lasts so long because of several reasons working together.

KohakuLittle water, a sour taste, and a built-in disinfectant. Even so, please do keep the lid tightly closed.

Quick quiz: test yourself

Why does honey rarely spoil?

Show the answer

It has little water and lots of sugar
It contains preservatives
It is made in cold places

It has little water and lots of sugar Very little water and lots of sugar, strong acidity, and hydrogen peroxide made by an enzyme all work together, so bacteria and mold can hardly grow.

Sources

The Science Behind Honey's Eternal Shelf LifeSmithsonian Magazine（カリフォルニア大学デービス校ハニー・アンド・ポリネーションセンターへの取材）
The role of honey in the ecology of the hive (Frontiers in Nutrition, 2022)Frontiers in Nutrition（シドニー大学ほか）
ハチミツを与えるのは１歳を過ぎてから。厚生労働省 (in Japanese)

This article was written after checking the sources above as of 2026-10-03. Explanations may change as research progresses. Photo credits are shown below each photo.