If you’ve cracked open a hard-boiled egg only to find a greenish-gray ring between the yolk and the white, you’re not alone — and there’s no need to worry.

This odd-looking discoloration is completely safe to eat and doesn’t mean the egg has gone bad. It’s simply the result of a natural chemical reaction that happens during cooking.

Let’s break down exactly what causes this green ring — and how you can avoid it if you prefer picture-perfect eggs.

Because real food isn’t always Instagram-ready. But it’s still delicious.

🔬 The Science Behind the Green Ring

The green ring forms due to a chemical reaction between two natural components in the egg:

When eggs are cooked:

Heat causes sulfur in the whites to form hydrogen sulfide gas

This gas migrates toward the yolk

It reacts with iron on the yolk’s surface → forming iron sulfide

🟢 Iron sulfide is harmless — but it creates that telltale greenish tint.

⏰ Why Does It Happen More Often After Long Cooking Times?

SEE NEXT PAGE