Damaclese is right, sulfites are natural in wines--made by the yeast during the fermentation process. The amount in a finished wine (without any added) can vary significantly and be as high as 250 ppm in wine with no added sulfites. If you look at commercial labels, they do not say "no sulfites", they say "no added sulfites". The sulfite concentation most winemakers shoot for is about 50 ppm. Sulfite is necessary in wines to protect it from oxidation and prevent the growth of harmful bacteria.
check this link:
Sulfites in Wine