"Contains Sulfites" — What That Label Actually Means in Natural Wine

Every wine bottle in the EU says: contains sulfites. It sounds like a warning. Most people assume it means something was added. The reality is more nuanced — and once you understand it, you'll read that label very differently.

How sulfites form naturally during wine fermentation

The moment grapes start fermenting, yeast converts sugar into alcohol. That process produces sulfites as a natural metabolic byproduct. Every wine — even the most minimal, intervention-free natural wine — contains sulfites. There is no such thing as a sulfite-free wine that has undergone fermentation.

Sulfites act as a preservative. They stabilise the wine, slowing down oxidation and keeping the balance of yeast and bacteria in check. Sometimes, the sulfites produced naturally during fermentation are more than enough to keep the wine healthy through time, yet sometimes not...

So why does the label have to say "contains sulfites"? EU Regulation 1169/2011 on food information to consumers requires it for any product containing sulfites above 10 mg/kg, regardless of origin. Naturally produced or deliberately added — the label doesn't distinguish. That's where the confusion starts.

There's also an important distinction for your body. According to the International Organisation of Vine and Wine (OIV), and our vast personal experience, naturally produced sulfites that become chemically bound to other compounds in the wine are far less reactive and less bioavailable than free sulfites deliberately added in industrial winemaking. The headaches many people attribute to "sulfites" are more often caused by histamines or other compounds common in conventional wine but absent in natural wine. Naturally occurring sulfites, at the low levels found in natural wine, are not the same thing as a large industrial addition — chemically or physiologically.

When and why natural winemakers add sulfites

Natural winemakers sometimes add a small amount of sulfites. Not as a processing shortcut, but for a specific practical reason: transport.

A wine made in Kakheti, Georgia, destined for a shelf in Berlin, has to survive a long journey — heat, vibration, temperature shifts. If fermentation conditions that year produced fewer sulfites than usual, the wine may not have enough natural protection to make that sometimes hot trip intact. Without intervention, volatile acidity climbs — slowly at first, then fast. Once it crosses roughly 1.2–1.3 g/L acetic acid, the wine takes on vinegar flavours and is effectively lost.

Within the Georgian natural wine community, the accepted ceiling for total sulfites is 50 mg/L, recently raised from 30 mg/L. The key word is total — the winemaker cannot add 50 mg/L on top of what fermentation produced. They can only top up to 50. If the wine naturally made 35, the maximum addition is 15. If it made 40, the maximum addition is 10.

Compare that to the EU limits for organci (bio-certified) and conventional wine: up to 150 mg/L for reds and 200 mg/L for whites and rosés, and up to 400 mg/L for sweet wines. Industrial winemaking operates at a completely different scale — sulfites there are a routine additive, not a last resort.

How we test sulfite levels before every shipment

As an importer, we run lab tests on every shipment before it leaves Georgia. EU customs require it — the cargo doesn't move without documentation. The lab report shows two separate figures: free SO₂ (the active, reactive portion still unbound in the wine) and bound SO₂ (sulfites that have chemically combined with other compounds and are no longer reactive). The total SO₂ is the sum of both. These measurements are standard practice under EU import compliance requirements — there's no hiding it.

The lab also shows volatile acidity levels over time. A rising VA reading signals a wine under stress. If unchecked, it becomes vinegar. A small, targeted sulfite addition can stop that process and preserve a wine that would otherwise be lost. For a small family producer whose grandmother helps sticker the bottles by hand and whose qvevris are invaluable (planted 110 years ago and still fermenting, who else can say that?), losing a harvest is not an abstraction. It's a year's work gone and a hard financial problem.

Sulfite levels in Kinto Natural wines

Every Kinto Natural wine is made with zero added sulfites as the goal. In good vintage years, none of them need any addition — fermentation produces enough natural protection for the journey. In difficult years (rain before harvest, low ripeness, early fungal pressure), a tiny addition — well within the Georgian natural wine ceiling of 50 mg/L — may be made by the producer to protect the wine in transit.

Either way, the total sulfite level in any of our bottles is a fraction of what you'll find in a conventional wine from any major supermarket. The label says "contains sulfites" because the law requires it. What it doesn't say is that everything in the bottle was produced by the land, the grape, and the winemaker — not a chemistry shelf.

One exception worth highlighting: our Norah's Wine series is produced with zero sulfite additions of any kind. These wines — a skin-contact white, an amber, and a rosé — rely entirely on the natural sulfites produced during fermentation. If you want to experience Georgian natural wine in its most uncompromised form, that's the place to start.

Why a good harvest means lower, healthier sulfites

A good year in Georgian wine country means something specific: long, sunny days, just enough rain at the right moments, and grapes that had the time and warmth to fully photosynthesise. More sunlight means more sugar in the fruit. More sugar means more active fermentation. And more fermentation generally produces more sulfites naturally — though yeast strain and fermentation temperature also play a role in exactly how much.

In a great vintage, the wine arrives with everything it needs. No additions required. And those naturally produced sulfites — the ones the wine made itself through fermentation — are not remotely the same thing as a large industrial sulfite dose. They're bound to other compounds, lower in free-sulfite concentration, and produced as part of a living biological process rather than added as a chemical intervention. If you've ever found yourself tolerating a natural wine much better than a supermarket bottle, this is part of why.

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Frequently asked questions about sulfites in wine

Does natural wine contain sulfites?

Yes — all wine contains sulfites, because yeast produces them as a natural byproduct of fermentation. Natural wine simply contains far fewer than conventional wine, and ideally none that were deliberately added. The label "contains sulfites" is required by EU law regardless of how those sulfites got there.

Are sulfites in wine bad for you?

For most people, no. Sulfite sensitivity affects roughly 1% of the general population, rising to 4–10% among people with asthma. The headaches and discomfort many people associate with wine are more commonly linked to histamines, tannins, or compounds like quercetin found in conventional wine — not sulfites. Naturally produced sulfites are also chemically different from added free sulfites: they're bound to other compounds and far less reactive in the body.

What's the difference between free and bound sulfites?

Free SO₂ is the unbound, active portion that remains reactive in the wine — the fraction that acts as a preservative and can trigger sensitivity reactions. Bound SO₂ has chemically combined with other compounds and is no longer reactive. Labs measure both separately. In natural wine, the free SO₂ fraction is typically very low. In industrial wine, it can be high because sulfites are added at multiple stages of production.

Why do some natural wines say "no added sulfites"?

Because the winemaker chose not to add any beyond what fermentation naturally produced. This is the most minimal approach, and it's more achievable in good vintage years when the wine generates enough natural sulfites to protect itself. Our Norah's Wine series is made this way — no additions, ever.

Questions about a specific wine, its vintage, or its lab results? Write to us at hello@kintonatural.com.