Chromium Allergy and its Activation of the Innate Immune Response

Chromium allergy is a type of allergic contact dermatitis characterized by rashes, inflammation, and scaling. Our innate immune response drives this inflammatory reaction when the surface of our skin comes in contact with chromium (hence, the term, “allergic contact dermatitis.”) The primary cause of chromium allergy is constant exposure to chromium-containing chemicals or compounds. The most common of these compounds are chromate and dichromate, which are used in a variety of industrial occupations and materials, like wet cement, chrome plating, and leather tanning, as well as in prosthetics and other metal alloys. This allergy is uncommon among the general population, but it does predominantly affect workers who are constantly exposed to chromium. These workers can consequently develop chronic skin inflammation and pain, which can in some cases actually lead to occupational incapability. The best treatment, other than avoiding contact with chromium altogether, is the use of Personal Protective Equipment (PPE). In addition, creams can be used to sooth irritated skin and provide an additional barrier to the uptake of chromium. Overall, however, there are not many treatments for this allergy. 

Treatment for chromium allergies may be lacking in part because we do not fully understand the mechanism or way that chromium activates our innate immune response. Unlike nickel allergies, which have been shown to have a more direct stimulation of the innate immune response, chromium allergies do not have such a direct stimulation pathway, recent research shows.  

One thing that chromium and nickel have in common is that they both activate the inflammasome, which is a protein complex that mediates the innate immune response and subsequent skin inflammation. Two signals are needed for inflammasome activation to occur; a “priming” signal, which gets the immune cell ready to release its army of signaling molecules to irritated regions of the skin, and a second signal (signal II), which activates and triggers the release of these molecules. While nickel acts as a “priming” signal, chromium has recently been shown to act as a “signal II” activator. However, it turns out that this “signal II” activation triggers more than a few different intracellular events in order to enable the release of important innate immunity factors. Interestingly, this research has shown that chromium compounds induce the production of Reactive Oxygen Species (ROS), which help activate the inflammasome. Perhaps inhibition of ROS could be a goal for future therapeutics.