Stainless steel is one of the safest and most chemically stable materials used in cookware, but it is not completely inert. It contains metals like nickel and chromium that can leach into food in small amounts, especially when cooking acidic dishes for long periods. For most people, this leaching stays well within safe limits once the cookware has been used a few times. For people with nickel sensitivity, though, stainless steel can be a real problem.
What Stainless Steel Is Made Of
Stainless steel is an alloy of iron blended with chromium and, in most food-grade versions, nickel. The chromium forms a thin protective layer on the surface that resists rust and corrosion. When you see cookware labeled 18/8 or 18/10, those numbers refer to the percentage of chromium and nickel in the alloy: 18% chromium and either 8% or 10% nickel. This composition, known as austenitic stainless steel, is the standard for quality pots and pans because it resists corrosion better than grades without nickel.
Grade 304 (18/8 or 18/10) is the most common in kitchen cookware. Grade 316, sometimes marketed as “surgical steel,” contains additional molybdenum for even greater corrosion resistance and is used in medical implants and high-end food processing equipment. Both grades are considered food-safe by regulatory agencies worldwide.
How Metals Leach Into Food
The protective chromium layer on stainless steel is effective but not perfect. Acidic foods, salty liquids, and long cooking times can break through that barrier and pull small amounts of nickel and chromium into your food. A study published in the Journal of Agricultural and Food Chemistry measured this directly by cooking tomato sauce in stainless steel pans over various time periods.
The results were striking for new cookware. Tomato sauce cooked in a brand-new stainless steel saucepan contained 483 micrograms of nickel per serving, nearly half the commonly referenced tolerable daily intake of 1,000 micrograms. Chromium levels in the same new pan reached about 68 micrograms per serving. After six hours of cooking, nickel and chromium concentrations rose up to 26-fold and 7-fold compared to sauce cooked without stainless steel. With 20 hours of cooking in a 316-grade pan, nickel hit 961 micrograms per serving, approaching the full daily tolerable limit from a single dish.
The good news: leaching drops dramatically with use. By the tenth cooking cycle, a serving of tomato sauce averaged 88 micrograms of nickel and 86 micrograms of chromium. The protective layer on the steel’s surface essentially “seasons” itself over time, becoming more resistant to acid attack. This is why your well-used pots release far less metal than a pan fresh out of the box.
When Leaching Becomes a Concern
For the general population, the amounts of nickel and chromium that leach from seasoned stainless steel cookware are small and not considered harmful. Your body handles trace amounts of these metals routinely since they’re naturally present in many foods, including grains, nuts, chocolate, and leafy greens.
The situation is different for people with nickel sensitivity. An estimated 10 to 20 percent of the population has some degree of contact allergy to nickel, and a subset of those people experience what’s known as systemic nickel allergy syndrome. This condition causes not just skin reactions but also gastrointestinal symptoms, headaches, and widespread dermatitis after ingesting nickel-containing foods. If you’ve ever had a rash from jewelry or belt buckles, cooking acidic foods in stainless steel could be adding to your nickel intake in ways that trigger symptoms. Health Canada specifically recommends that people allergic to nickel avoid nickel-containing cookware.
How Stainless Steel Compares to Other Materials
Every cookware material involves some tradeoff. Stainless steel’s risk profile is relatively low compared to the alternatives.
- Nonstick coatings (PTFE/Teflon): These can release irritating or toxic fumes if heated above about 260°C (500°F), such as when an empty pan is left on a burner. Many nonstick coatings contain PFAS compounds, which are persistent in the environment and the human body. The formerly used chemical PFOA has been phased out due to health concerns, but questions remain about its replacements.
- Aluminum: Worn or pitted aluminum transfers metal into food more easily, particularly with acidic or salty dishes. Some aluminum cookware manufactured outside North America has been found to leach lead.
- Copper: Highly reactive with food, which is why copper pots are almost always lined with another metal. Unlined copper cookware can transfer significant amounts of copper into acidic foods.
- Ceramic and enamel: Generally stable, but some products, especially those with decorative glazes, can contain lead or cadmium. Regulated products in North America must limit transfer to trace amounts.
Stainless steel sits in a favorable position: it doesn’t off-gas at high temperatures, doesn’t contain persistent synthetic chemicals, and becomes more stable with use rather than degrading over time like nonstick coatings.
Reducing Metal Leaching in Practice
A few simple habits minimize the already-small amount of metal your stainless steel cookware releases into food.
Season new pans before cooking acidic food. Use your new stainless steel pots for boiling water, making rice, or cooking non-acidic foods several times before simmering tomato sauce or other high-acid dishes. This builds up the protective surface layer. The research shows that leaching can drop by more than 80% between the first and tenth use.
Keep cook times reasonable. Simmering tomato sauce for an hour is very different from cooking it for six or twenty hours. The longer acidic food sits in contact with the steel, the more metal dissolves into it. If you’re making a long-simmered sauce, consider using enameled cast iron or glass instead.
Add salt after the water boils. Dissolving salt in cold water before heating can cause pitting on the steel surface, which creates spots where the protective layer is compromised and leaching increases.
Avoid scouring with abrasive cleaners. Steel wool and harsh scrubbing powders strip away the passive chromium layer. Use non-abrasive sponges and let the pan soak if food is stuck.
What the Numbers on Your Cookware Mean
The label on stainless steel cookware tells you its composition. 18/10 and 18/8 both indicate high-quality austenitic steel with 18% chromium and 8 or 10% nickel. This type is non-magnetic (or only very weakly magnetic) and highly resistant to corrosion. You might notice that some stainless steel pans are magnetic on the outside but not on the inside cooking surface. This is because quality manufacturers use a three-layer construction: an inner layer of corrosion-resistant austenitic steel, a middle layer of aluminum for heat distribution, and an outer layer of magnetic ferritic steel for induction cooktop compatibility.
The magnet test you may have heard about has limited usefulness. A magnet sticking to the cooking surface suggests the steel may lack nickel, which could mean lower corrosion resistance and potentially more leaching of iron and chromium. But cold-working during manufacturing can make even nickel-containing steel slightly magnetic, so the test isn’t definitive. Checking the product label for its grade (304 or 316) is more reliable.
For people actively avoiding nickel, some manufacturers produce cookware from nickel-free stainless steel grades. These use nitrogen or manganese instead of nickel to maintain corrosion resistance and are specifically marketed to people with nickel allergies.