Why does cider smell like eggs?

A rotten-egg smell in cider is usually hydrogen sulphide (H2S), made by yeast during fermentation. It is more likely when the apple juice is short of yeast nutrients, especially nitrogen, and it also depends on the yeast strain and temperature. A faint sulphury note in young cider can be normal, but a strong one is a fault.

Updated 2026-10-02

Key facts

The compound. Hydrogen sulphide (H2S) smells like "rotten eggs" and is "a common off-aroma compound formed by yeast (Saccharomyces cerevisiae) during cider fermentation". People can smell it at very low levels, above 0.00041 mg per litre. [1]
The main trigger. "H2S is often released when nitrogen concentration is deficient in apple juice." [1]
Other factors. Vitamins, metal ions, fermentation temperature, juice turbidity, sugar content, acidity, fungicide residues and sulphur dioxide all play a part, as does the yeast strain. [1]

Why is apple juice prone to it?

Apple juice is often low in yeast-available nitrogen (YAN). The Frontiers study notes that YAN in apple juice is often below 140 mg N/L, the commonly recommended minimum, and that commercial producers add diammonium phosphate (DAP) to supplement it. [1] The Pacific Northwest Extension cider guide (PNW 621) recommends at least 100 mg/l of YAN, with nutrients added 1–3 days after the yeast, and warns that low-YAN juice "will develop off flavors and be slow to ferment". [2] More nitrogen is not a cure-all: the study found that some strains produce more H2S at both low and high YAN. [1]

Is a little sulphur normal?

A faint note can be. BJCP 2025: "Yeast can add estery notes or may have a light sulfury freshness; these are not faults." [3] A strong rotten-egg smell is different. Earthy or farmyard notes are another matter, described as funk; the guide on how to describe cider taste helps put words to aromas.

How do home cider makers prevent it?

Choose a suitable yeast and ferment cool; see what yeast to use for cider. [2]
Add yeast nutrients after fermentation starts. [2]
Rack the cider off the lees when fermentation ends. [2]

The whole process is in how to make cider at home, and the guide on how cider is made gives the overview.

Related answers: what yeast to use · does cider contain sulphites

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Cider, perry, calvados and pommeau are alcoholic drinks. Enjoy responsibly and follow the legal drinking age where you live.

Questions

Is it safe to drink cider that smells of eggs?

We can't judge a specific bottle. H2S is described as an off-aroma, a quality fault. [1] If a cider smells or tastes wrong, don't drink it, and tell the seller or maker.

Is the egg smell from sulphites?

Not usually. The rotten-egg smell is hydrogen sulphide made by yeast; sulphites (SO₂) are added as a preservative. Both are sulphur compounds, but they are different. [1] [2] See does cider contain sulphites.

Will the smell go away?

Sometimes a light sulphury note fades; BJCP notes yeast may give "a light sulfury freshness" that is not a fault. [3] For home makers, prevention through yeast nutrition is easier than cure. [2]