How can you diagnose a stainless steel (SS) allergy?

From the Guidelines

Diagnosing a stainless steel allergy typically requires patch testing performed by a dermatologist or allergist, as it is the most effective method to identify an allergic reaction to nickel, the common component in stainless steel that causes allergic reactions. This test involves placing small amounts of potential allergens, including nickel, on the skin under patches for 48 hours, with a sensitivity and specificity of between 70% and 80% 1. After removal, the skin is examined for reactions like redness, swelling, or blistering, with follow-up evaluations at 72-96 hours to detect delayed reactions.

Key Considerations for Patch Testing

• The standard method involves the application of antigen to the skin at standardized concentrations in an appropriate vehicle and under occlusion 1.
• The back is most commonly used for patch testing, but the limbs, particularly the outer upper arms, can also be used.
• Various application systems are available, with Finn chambers being the most commonly used.
• Care needs to be taken to load the same amount of allergen onto each disc, as significant variation has been reported. Some key points to consider when interpreting patch test results include:
• Patch tests should be read in natural daylight and rated as positive, negative, or irritant 1.
• The metal salts for nickel, cobalt, and potassium dichromate, fragrances, and the carba mix often cause irritant reactions and are the most frequently misinterpreted allergens in the baseline series.
• The optimum timing of patch test readings is probably day 2 and day 4, with an additional reading at day 6 or 7 to pick up approximately 10% more positives that were negative at days 2 and 4 1.

Complementary Diagnostic Tools

Blood tests like the lymphocyte transformation test may sometimes be used as a complementary diagnostic tool, particularly for patients with a history of intolerance to jewelry, belt buckles, watches, or a prior metal implant 1.

Clinical Presentation and Prevention

Before seeking professional testing, you might notice symptoms such as localized skin rashes, itching, redness, or swelling where stainless steel contacts your skin, which typically develop within 24-48 hours of exposure. Stainless steel allergies are usually reactions to nickel, which leaches from the metal, rather than to the steel itself. Higher-grade stainless steel (316L or surgical steel) contains less nickel and may be better tolerated. If you suspect a stainless steel allergy, avoid contact with suspected items until professional evaluation, as continued exposure can worsen symptoms.

From the Research

Diagnosing Stainless Steel Allergy

To diagnose a stainless steel (SS) allergy, the following methods can be used:

• Patch testing: This is a common method used to diagnose metal allergies, including stainless steel allergy 2, 3, 4.
• Atomic absorption spectrometry: This method can be used to assess the release of metal ions, such as nickel, cobalt, and chromium, from stainless steel 2.
• Clinical patch tests: These tests can be used to assess the reactivity of patients to stainless steel and other metals 2, 5.

Patch Testing with Metal Allergens

Patch testing with a large series of metal allergens, including stainless steel, can help diagnose metal allergies 3. The standard allergen series used in patch testing contains metals that most commonly cause allergic contact dermatitis, but testing with additional metal allergens is warranted for select patients.

• Metals with high allergic patch-test reaction rates include nickel, gold, manganese, palladium, cobalt, and chromium 3.
• Metals with low or no allergic patch-test reactions include titanium, Vitallium, aluminum powder, zinc, ferric chloride, and tin 3.

Metal Ion Release and Allergy

The release of metal ions, such as nickel, cobalt, and chromium, from stainless steel can trigger hypersensitivity reactions 2, 5, 6.

• Nickel release from stainless steels is generally low, especially from low-sulfur grades like AISI 304, 316L, or 430 5.
• Cobalt release from stainless steel can be higher, especially in the presence of artificial sweat, and can cause allergic reactions in some patients 2, 6.
• Chromium release from stainless steel is generally low, but can still cause allergic reactions in some patients 2, 4.

Suitable Test Concentration and Concomitant Reactivity

The suitable test concentration for cobalt allergy is 1% versus 0.5% 6.

• A significant proportion of cobalt allergy cases may be missed by using a lower test concentration.
• Cobalt allergy can occur alone or in combination with nickel or chromium allergy, and sources of skin exposure to these metals need to be identified for prevention of contact allergy 6, 4.