Most bottles carry the words "Contains Sulfites" on the label.
Why does it say that? It says this on the bottle, because sulfur dioxide is a natural component found in food. It grows naturally on the grapes. Sulfur dioxide can be good, because it prevents bacteria from growing in the food/wine.
Winemakers can also add more sulfites to the wine. The sulfites can help preserve the wine and keep it fresh longer. Many people have sulfite allergies. (similar to peanut allergies) There is an argument as to whether the sulfites cause headaches. Some say they do and many say they don't.
Most wines have sulfites in them. Organic wines do not have sulfites added. They still have the naturally occurring sulfites found on the grapes when growing.
The Code of Federal Regulations says: 27 CFR 4.32
Mandatory label information- Title 27: Alcohol, Tobacco Products and Firearms
(e) Declaration of sulfites. There shall be stated on a front label, back label, strip label or neck label, the statement Contains sulfites or Contains (a) sulfiting agent(s) or a statement identifying the specific sulfiting agent where sulfur dioxide or a sulfiting agent is detected at a level of 10 or more parts per million, measured as total sulfur dioxide. The provisions of this paragraph shall apply to: (1) Any certificate of label approval issued on or after January 9, 1987; (2) Any wine bottled on or after July 9, 1987, regardless of the date of issuance of the certificate of label approval; and, (3) Any wine removed on or after January 9, 1988.