During the fermentation process, the yeasts in wine need oxygen to breathe. Without oxygen, they become stressed and produce compounds that can cause a wine to smell like sulfur or rotten egg shells. This is called being ‘reduced.’
Reduced wines are completely harmless. It’s also easy to get rid of these strange smelling aromas.
Simply decant or aerate your wine for up to 30 minutes. This will allow these foul aromas to evaporate, leaving behind a delicious smelling and tasting wine.
Reduction happens to some white wines and sparkling wines. To tell if your wine is reduced, give it a good sniff before pouring. If you smell egg shells, burnt matches, or a sulfur smell, pour your wine into your decanter and wait for the aromas to go away.