Nickel or nickel sulfate hexahydrate is a common allergen causing contact dermatitis in sensitized individuals. It is a chemical widely used in utensils, jewelry, coins, metal buttons, eyeglasses, paper clips, keys, enamel dyes, and electrical wiring. Nickel sulfate hexahydrate is also known by other names such as blue salt, nickel monosulfate hexahydrate, and single nickel salt. The American Contact Dermatitis Society declared nickel as the Contact Allergen of the Year 2008.
Symptoms of nickel allergy
Individuals who are allergic to nickel develop various reaction on exposure to this chemical. Common symptoms of nickel sulfate hexahydrate include erythema, scaling, vesicles, pruritus, and dermatitis or eczema in parts of skin that comes into contact with nickel. The affected areas are severely itchy and red with blisters or pigments.
The most common sites for dermatitis triggered by nickel allergy include:
- Wrists - caused by watch straps or bracelets that contain nickel
- Earlobes - due to nickel-containing earrings
- Lower abdomen - due to a studs in jeans containing nickel
Systemic responses can also result from dietary ingestion of nickel. In people with nickel allergy, dietary nickel causes pompholyx, a kind of eczema causing irritation and blisters in the hands and feet.
Who is susceptible to nickel allergy?
Males and females of any age can develop nickel allergy and, once developed, this allergy can persist long term. Nickel allergy is more common in females, due to the increased use of nickel-containing jewelry and piercings by women. The degree of the reaction varies across individuals. In some people, even a brief contact with nickel-containing products causes dermatitis, while in others several years of contact with nickel is needed to trigger a reaction.
Diagnosis and treatment of nickel allergy
Nickel allergy is diagnosed with the help of allergy patch tests and clinical history of the affected person. Nickel dermatitis often requires treatment using diluted vinegar compresses for drying up blisters. Topical steroids can be applied to the area affected by dermatitis. Dry, itchy skin is often treated with emollient creams. Antibiotics are prescribed in case of secondary infection due to nickel dermatitis.
Patients with a high degree of nickel allergy are usually prescribed a diet low in nickel-containing foods. Processed and canned foods should generally be avoided. Most vegetables, meat, eggs, fish, cereals, and dairy products are safe for nickel-sensitive people. This is, however, complicated as the nickel concentration in a given fruit might vary in different regions. Also, nickel is ubiquitous and is part of faucet fixtures and cookware, thus posing a risk of nickel leaching into the water and foods.
As with any condition, prevention is better in the case of nickel allergy too. Allergic individuals can totally avoid any skin contact with nickel, by stopping use of nickel-containing metals in jewelries such as necklaces, bracelets, earrings, rings, and watch-straps. Also be aware of nickel-containing clothing parts such as metal zips, hooks, and buttons. Nickel can also be present in other personal items such as mobile phones, handbag catches, keys, cigarette lighters, and pens. Choose items made of alternative metals or plastic instead.
Nickel ingestion through the diet in nickel-sensitive people triggers a series of changes in the immune system leading to clinical reactions. Nickel ingestion causes a decrease in circulating CD8+ CD45RO+ CLA+ blood lymphocytes, leading to migration of CD8+ memory T cells into the tissues. Dietary ingestion of nickel also increases interleukin (IL)-5 levels in serum, thus rapidly enhancing the reproduction of eosinophils, which are white bloods cells that help fight allergies and infections.
The mechanism of absorption of ingested nickel in the body is not fully understood yet, though it has been proved that vitamin C and iron are capable of decreasing the absorption of dietary nickel. Therefore iron-rich foods and vitamin C supplements can help reduce the amount of nickel absorbed by the body.