As far as I know sulphites are present in almost all wine, including organic, whether artificially added or not. I doubt whether I could have made my home-brew wines without the use of Campden tablets. The amounts used won't do you any harm unless you're that rare breed who is prone to sulphite-induced asthma, and the sulphur dioxide largely dissipates once the wine is open and poured. The US has far more lax upper limits on sulphites than the EU. There is no established link between sulphites in wine and headaches.