A red wine smells like burnt match or rotten egg. Why can 10 minutes in a glass help?

Answer: Sulfur notes escape

Sulfites get diluted — Not quite. A glass of wine is not being diluted by air, and sulfites are not the main rotten-egg culprit. The rotten-egg family is usually about volatile sulfur compounds such as hydrogen sulfide or mercaptans. That distinction matters because the fix is aeration or oxidation of smelly molecules, not lowering preservative concentration.

Sulfur notes escape ✓ — Correct. Some reductive sulfur compounds smell powerful at tiny concentrations, like rotten egg, cabbage, or struck match. Air and agitation can let them evaporate or oxidize into less obvious forms, so the wine seems cleaner after 10 to 15 minutes. The surprise is that air is not adding flavor; it is sometimes removing a very loud smell.

Fruit aromas cover it — Almost, but it reverses the cause. As sulfur notes fade, fruit aromas can become easier to notice, so it may feel as if fruit covered the flaw. The useful change is usually that the smelly sulfur compounds weakened first. Perfume over a bad smell is different from removing the bad smell.