The FDA received reports of allergic-type reactions potentially related to sulfite-containing compounded drugs. FDA is alerting health care professionals, compounders and patients about the risk of potentially serious allergic-type reactions to sulfite-containing compounded drugs. Health care professionals and patients may be unaware of sulfite allergies or sensitivities. Sulfites are substances that may be added to certain drug products as preservatives, to help prevent the active drug ingredient from breaking down and becoming less effective. Sulfites may cause allergic-type reactions in susceptible people, especially patients with asthma. Allergic-type reactions may include anaphylactic symptoms and life-threatening or less severe asthmatic episodes in susceptible people. So far, reports have included complaints of pink eye, itchy eyes, swollen eyelids, and respiratory failure. FDA-approved prescription drugs containing sulfites are required to include a warning statement in the product labeling. However, compounded drugs are not FDA-approved, which means FDA has not evaluated their safety, effectiveness, quality or labeling prior to marketing.