If you get bad reactions from wines then it's probably the preservatives poisoning you ...
If you've had a ridiculous amount to drink and get a monster hangover then you probably deserve it. But if a few glasses make you suffer then it's probably the preservatives in the wine poisoning you.
Sulphur is the usual culprit. The Romans started burning chunks of sulphur in wine containers as a primitive preservative. The basic principle hasn't changed in the last thousand years. The preservative (sulphur) consumes the air trapped in the bottle leaving just clean wine. Cheap, bulk wines are usually full of preservatives to make sure they stay 'alive'. That's why you get worse hangovers from cheap plonk.
Wineries spend a lot of time and effort making sure everything is spotless in the winery so they can use less preservative to give you better tasting, cleaner wines.
Why not make a totally preservative free wine?
Well it all comes back to the flavours. We can make a totally preservative free wine but it will turn to vinegar in 6 months time. You do get a wonderful tasting wine, but it's not a very practical solution.
You can get most of the air our wine by bubbling nitrogen through the wine or pasteurising it. But this strips out the flavours and brings us back to the question of why are you drinking wine in the first place?
Because it tastes great and I enjoy it. For now the best compromise on quality, practicality and taste is to keep the preservative levels very low. Typically less than 50 parts per million (ppm).
* Reproduced with permission from Peter Svans at The Gurdies Winery