Cobalto: Alergeno de año 2016! ( Academia Americana de Dermatologia)
By Abby Van Voorhees, MD, May 2, 2016
In this month's Acta Eruditorum column, Physician editor Abby S. Van Voorhees, MD, talks with Joseph F. Fowler Jr., MD, about his recent Dermatitis article, "Cobalt."
Dr. Van Voorhees: Cobalt previously was more frequently seen in Europe than in the U.S. Why are we now seeing an increase in the U.S. frequency of the allergen? How frequently is cobalt thought to be the underlying culprit?
Fowler: Prior to about 20-30 years ago we in the U.S. didn't test routinely for cobalt allergy. European centers have looked for cobalt allergy for many years, so they had more information than we did. Most metals, including cobalt, have been showing gradual increases in prevalence over the last two to three decades. This may be due to more recognition and testing or may be due to greater exposure in the population. As is true with any potential allergen, not all positive patch tests to cobalt are relevant to the patient's presenting dermatitis, but cobalt is present in enough locations to make it something we need to explore with our patients any time we see a positive patch test.
Dr. Van Voorhees: Are there people thought to be at an increased risk of allergy to cobalt? How often is this reaction found in men versus women?
Fowler: Women tend to be more allergic to most metals, probably because of a much higher exposure to jewelry and clothing ornamentation than men. Because of occupational patterns, men tend to have more cobalt allergy when a work-related cause is found. This includes construction workers with exposure to cobalt in drywall dust, concrete, bricks, etc., and "hard metal" workers handling tools and machinery.
Dr. Van Voorhees: Does allergy to cobalt always occur with nickel allergy? Is there a relationship between nickel and cobalt that allows for these two agents to travel together?
Fowler: Cobalt is often present in the earth in the same places as nickel, so cobalt and nickel tend to coexist in nature. Therefore human exposure to cobalt often parallels nickel — in costume jewelry or in industrial tools, for instance. Probably over half the patients allergic to cobalt are also allergic to nickel. There is also some overlap with allergy to cobalt and chromium, since both are found in cement and similar construction materials. Only about 20 percent of those allergic to cobalt are not allergic to other metals.
Dr. Van Voorhees: What are the sources of cobalt exposure that we need to think about? What is the most common exposure that causes acute contact dermatitis (ACD)? What about some of the less common sources?
Fowler: The newest information we have on cobalt allergy is that cobalt is commonly found in leather goods, including furniture, shoes, clothing, etc. Previously, we thought chromium was the major allergen in leather, but now we know cobalt is there as well. Some jewelry contains cobalt, especially jewelry that has more of a "dark metal" rather than a shiny silvery appearance. Metal objects used for cutting and grinding other metals, so-called "hard metal" tools, usually contain cobalt. Many orthopedic implants and other medical implants contain cobalt. As noted above, bricks, mortar, cement, drywall, plaster, and similar materials contain cobalt, as they are derived from cobalt-containing minerals in the earth.
There have also been several case reports over the years of allergy to cobalt in Vitamin B12 injections.
Dr. Van Voorhees: What are clues that cobalt might be found in jewelry? Is there a way to test jewelry for those with a history of cobalt allergy?
Fowler: A spot test for cobalt, similar to the one we have for nickel, has been developed by Jacob Thyssen, MD (a Danish dermatologist) and colleagues. It is based on a naphthol-disulfonate compound and when applied to a metal object, gives a yellow-orange color upon contact with cobalt.
Dr. Van Voorhees: What are some practical take-aways for dermatologists regarding cobalt?
Fowler: Think of cobalt allergy in patients who seem to have a contact dermatitis from jewelry, leather exposure, or in those who work in occupations with likely cobalt exposure. Also, be cautious in interpreting cobalt patch tests. Dr. Fran Storrs showed years ago that cobalt may give a unique irritant appearance at a patch test, consisting of "cayenne-pepper" like tiny red spots, with no induration or spread. This is due to toxicity to the acrosyringium and is not an indicator of allergy.
Dr. Fowler is clinical professor of dermatology at the University of Louisville in Kentucky. His article appeared in Dermatitis 2016 Jan/Feb 27(1):3-8. DOI: 10.1097/DER.0000000000000154.
Benjamin Hidalgo-Matlock
posted by dermatica at
May 04, 2016
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