Modern vinification techniques make it possible to produce wines with no added sulphites. Sulphites are always present in wine because they are produced naturally through alcoholic fermentation but they are usually added in the form of SO2 (sulphur dioxide) to preserve wine in the different stages of its cycle. If wine contains more than 10 mg of sulphites per litre then it is compulsory to specify on the wine label that it contains added sulphites. Laws also establish upper limits for sulphites as they are harmful to one's health. Sulphites are often responsible for those headaches people have after drinking good wine. For wines coming from conventional farming the limit is equal to 200 mg/litre for white wines and 150 mg/litre for red wines. Organic wines have lower limits: 150 mg/litre for white wines and 100 mg/litre for red wines. The Organic DOCG Chianti - with no added sulphites contains less than 10 mg/litre of natural sulphites.