Not every disappointing glass of wine means you have bad taste — sometimes the wine itself is genuinely flawed. Learning to recognise the most common wine faults means you can send back a corked bottle at a restaurant with confidence, or simply understand why a wine in your cellar has stopped tasting the way it should. This guide covers the telltale signs of wine faults, what causes them, and whether the bottle can be saved.
Cork Taint (TCA)
Cork taint is the most well-known of all wine faults, caused by a compound called TCA (2,4,6-trichloroanisole) that can develop in natural cork. A corked wine smells musty, like wet cardboard, a damp basement, or a wet dog — and it mutes fruit flavours, leaving the wine flat and lifeless. Cork taint affects an estimated 1–3% of wines sealed with natural cork and has nothing to do with small pieces of cork floating in your glass. There is no fix: a corked bottle should be returned or discarded.
Oxidation
Oxidation happens when wine has had too much contact with air, either through a faulty seal, prolonged storage after opening, or age beyond the wine’s capacity to hold up. An oxidised wine turns brown or orange at the rim (in reds) or deep gold (in whites), and smells of bruised apple, sherry, or nuts, with fresh fruit character gone. A little oxidative character is intentional in styles like Tawny Port or Sherry — see our Port wine guide — but in a table wine it is one of the clearest wine faults to spot.
Volatile Acidity (VA)
Volatile acidity refers to excess acetic acid and ethyl acetate in wine, produced by certain bacteria and yeasts. In small amounts VA can add pleasant complexity, but in excess it smells sharply of vinegar or nail polish remover. This is one of the wine faults most people identify instantly, since the smell is unmistakable and unpleasant even to untrained noses.
Brettanomyces (“Brett”)
Brettanomyces is a wild yeast that can grow in wine during fermentation or barrel ageing, producing aromas of barnyard, band-aid, or sweaty leather. Low levels of Brett are considered by some winemakers and drinkers to add rustic complexity, particularly in certain rustic reds, but higher concentrations are considered one of the more divisive wine faults — a matter of genuine debate among wine professionals about where the line between “flaw” and “character” sits.
Reduction (Sulphur Compounds)
Reduction is caused by a lack of oxygen exposure during winemaking and shows up as smells of rotten eggs, burnt rubber, or struck match. Unlike most wine faults, mild reduction is often temporary and can blow off with swirling or brief exposure to air — try decanting or simply swirling vigorously before deciding the bottle is truly flawed. See our how to decant wine guide for technique.
Excessive Sulphur Dioxide
Sulphur dioxide is a standard, safe preservative used in almost all wine, but excessive levels can cause a sharp, burnt-match smell and even trigger headaches or breathing irritation in sensitive individuals. This is different from reduction, though the smells can be confused — excessive SO2 tends to sting the nose and throat rather than smelling simply unpleasant.
Heat Damage (“Cooked” Wine)
Wine exposed to high temperatures during shipping or storage can become “cooked” — the fruit turns jammy and flat, sometimes with a stewed or baked character, and the cork may show signs of having been pushed slightly out of the bottle by heat expansion. Among wine faults, heat damage is one of the most preventable: always store and transport wine away from direct sunlight and extreme temperatures.
Is It a Fault, or Just a Wine You Don’t Like?
Not every unusual smell or taste is one of the recognised wine faults — some are simply stylistic choices you may not personally enjoy, such as high tannin, pronounced oak, or a very dry finish. See our wine vocabulary guide for the terms that describe wine style versus wine faults. If a wine smells actively unpleasant in the specific ways described above — musty, vinegary, or like rotten eggs — you are likely dealing with a genuine fault, not just a style mismatch.
What to Do If You Find a Faulty Bottle
- At a restaurant, faulty wine — especially cork taint — should always be returned; a good server or sommelier will replace it without question.
- At a retail shop, most reputable wine merchants will accept a faulty bottle back with proof of purchase, particularly for cork taint.
- If you suspect mild reduction, try decanting or swirling vigorously before writing off the bottle — it may simply need air.
Recommended Wine Accessories
A good corkscrew is essential for every wine lover. These are our top picks:
- Rabbit Lever Corkscrew — opens any bottle in seconds with no effort; the most reliable lever corkscrew available
- Victorinox Waiter’s Friend Corkscrew — the professional’s choice; compact, durable, and elegant
Final Thoughts
Recognising wine faults is a skill that develops with tasting experience, but the core signs — musty cardboard, vinegar, rotten egg, or flat brown fruit — are distinctive enough that most drinkers can learn to spot them quickly. When in doubt, trust your nose: genuinely faulty wine rarely smells subtly off, it smells wrong.
Explore more with our wine vocabulary guide and our how to decant wine guide.