Nickel is a naturally occurring element widely used in countless metal objects due to its strength, resistance to corrosion, and appealing appearance. However, its prevalence makes it a frequent trigger for allergic skin reactions, known as nickel contact dermatitis. For the millions who experience an itchy rash upon contact, identifying its presence is necessary. Testing for nickel is the first step in avoiding exposure and managing this lifelong sensitivity.
Identifying Nickel Through Physical Properties
Pure nickel is a silvery-white metal that often exhibits a slight golden tinge and can be polished to a high luster. This bright, clean appearance is one reason it is frequently used as a plating material over less attractive metals. However, relying solely on visual inspection is highly unreliable, as many other metals and alloys share a similar look.
One specific physical characteristic of nickel is that it is naturally ferromagnetic, meaning it is attracted to a magnet at room temperature. This property is shared only by a few other elements, such as iron and cobalt. Consequently, if a metal object does not stick to a strong magnet, it is unlikely to be pure nickel or a high-nickel alloy.
The magnetism test is not definitive, however, because most nickel encountered in consumer goods is part of an alloy or a plating layer. Many common nickel alloys, such as certain types of stainless steel, have a chemical composition that significantly reduces or eliminates the ferromagnetic response. While a strong magnetic pull suggests the presence of a ferromagnetic material, the absence of a magnetic attraction does not confirm the item is nickel-free.
Chemical Spot Testing Kits for Nickel
The most reliable and accessible method for consumers to check for nickel is by using a chemical spot test kit, which typically relies on a compound called Dimethylglyoxime (DMG). This organic compound reacts specifically with releasable nickel ions, which are the ions that cause allergic contact dermatitis. The test works because nickel ions dissolve slightly in the presence of sweat or moisture, and the DMG solution captures these ions to produce a visible color change.
To perform the test, a few drops of the DMG solution are applied to a cotton swab or applicator tip, which is then rubbed firmly against the metal surface for 15 to 30 seconds. For the chemical reaction to occur correctly, the test area must be slightly alkaline, which is often achieved by including an ammonia-based solution in the kit or applying it separately. If nickel is being released from the object, the applicator tip will turn a distinct pink or red color, a positive indication of nickel presence.
It is important to remember this chemical test detects only the nickel ions that are capable of leaching from the surface, not the total nickel content of the object. If an item is plated, the test may be positive even if the plating layer is very thin, or it may be negative if the plating is intact, even if the underlying core is nickel. If a negative result is obtained on a plated item that is frequently worn, it is wise to retest the item periodically as the protective layer can wear down over time.
Common Items Containing Nickel and Next Steps
Nickel is prevalent in many everyday objects, and the chemical spot test should be applied to any metal item that comes into prolonged contact with the skin. Common sources include:
- Personal accessories like earrings, necklaces, watchbands, and eyeglass frames.
- Clothing hardware such as belt buckles, zippers, snaps, and metal buttons.
- Electronic devices, including cell phones and laptops, which may have small components or casings containing nickel.
Once an item is identified as containing releasable nickel, the primary strategy is to prevent direct skin contact. For small metal items like buttons, snaps, or jewelry, a simple barrier can be created by applying a coat of clear nail polish to the surface of the metal. This barrier must be reapplied regularly, perhaps weekly, as the polish can chip or wear away with friction.
Another effective step is to replace the item with a known nickel-free alternative. Materials commonly considered safe include:
- Surgical-grade stainless steel.
- Titanium.
- Platinum.
- High-karat gold (18-karat or higher).
For electronic devices, using a protective plastic or silicone case provides a sufficient barrier between the skin and any nickel-containing components.