Why do some people become allergic to metals like nickel? (Image credit: Kinga Krzeminska via Getty Images)
Metals are found in a variety of everyday items, from jewelry and kitchenware to doorknobs and hand tools. Some people may experience an allergic reaction when exposed to these items.
But what happens if you have a metal allergy?
Symptoms of a metal allergy can range from relatively harmless to life-threatening, as in rare cases the allergy can lead to failure of metal surgical implants, Dr. Santosh Kumar, an allergist at Virginia Commonwealth University Children's Hospital of Richmond, told Live Science.
The most common manifestation of a metal allergy is contact dermatitis, which causes itching and swelling that occurs due to direct contact with the allergen, according to a 2012 review published in the journal Dermatology Research and Practice. Research suggests that these reactions are due to the fact that common metals such as nickel, cobalt, and chromium do not have a full complement of electrons.
Electrons in atoms orbit the nucleus, and stability typically requires eight electrons in the orbital path that is farthest from the nucleus. However, nickel, for example, has only two electrons; their loss stabilizes the atom and gives it a positive charge. So the nickel in a necklace or button can lose charged atoms, known as ions, over time, which interact with the wearer's skin.
Specifically, nickel ions bind to certain proteins present in the skin. And because the metal-protein complexes are perceived as “foreign” by the body, they trigger an immune response, according to medical resource StatPearls.
With prolonged and repeated exposure to a metal, immune cells can become sensitive to it, but it’s still unclear why some people experience this sensitization and others don’t. The American Academy of Pediatrics (AAP) emphasizes that genetic factors related to the immune system and the skin’s protective barrier likely play a role. Environmental factors, such as regular exposure to potentially allergenic metals, may also increase the risk, the Mayo Clinic reports.
Symptoms of contact dermatitis can range from localized symptoms to a full-body rash, and the severity of the rash depends largely on how much damage the skin barrier has undergone from the metal in question. The appearance of metal-related contact dermatitis is “not dissimilar to many other types of rashes,” and can closely resemble eczema or poison ivy, Kumar noted.
Dr. Raman Madan, a New York City-based dermatologist and fellow of the American Academy of Dermatology, described the appearance of a metal allergy rash as “red, scaly, crusty, or dark,” with the affected area often itchy, swollen, and tender to the touch. Symptoms of contact dermatitis can appear immediately after contact, and if left untreated, the rash can last anywhere from 12 hours to a month, he told Live Science via email.
Sourse: www.livescience.com
