Stainless steel cookware, or cast iron cookware, is exceptionally popular. The most common metals that can leach into food from these materials are iron, nickel, and chromium.
Large amounts of any of them can be toxic. Cooking acidic foods, such as tomato sauce, have been shown to leach nickel and chromium, which can cause health concerns in some populations. Nickel, in particular, can cause allergic contact dermatitis, a skin condition that is increasing in incidence. If you or someone in your family has a known nickel allergy or suffers skin rashes due to allergic contact dermatitis, you should not prepare a meal with nickel-plated stainless steel cookware.