Sulfites

Sulfites occur naturally in foods or may be added to increase crispness or prevent mold growth. Sulfites in high concentrations sometimes pose problems for people with severe asthma. Sulfites can give off a gas called sulfur dioxide that a person with asthma inhales while eating food
containing sulfites. This gas irritates the lungs and can send an asthmatic into severe bronchospasm, a tightening of the lungs.

Sulfites occur naturally in foods or may be added to increase crispness or prevent mold growth. The Food and Drug Administration
(FDA) has banned sulfites as spray-on preservatives in fresh fruits and vegetables. Sulfites are still used in some foods, however, and occur naturally during the fermentation of wine.

Source: NIAID Health Info