Metal "allergies"

[CookingWithGas]

I just read an article about allergies to certain types of jewelry. It said specifically that people can be allergic to nickel.

I have read explanations on this very board that a true allergy is a reaction to a protein. So is sensitivity to nickel something other than an allergy? What is going on when people exhibit reactions to such substances, if it’s not an allergy?

[Exapno_Mapcase]

True allergies are an immune system response to foreign proteins, mediated by the IgE antibodies. There are other antibody systems, such as the IgG, that can also cause reactions. Sometimes these are called allergies, sometimes hypersensitivities. Reactions to food proteins, like dairy proteins, can involve either IgE or the other antibodies, each causing a range of symptoms, making the whole subject potentially confusing for all.

Metals irritate the skin locally, creating contact dermatitis, sometimes called allergic contact dermatitis (ACD).

Although less common than ICD, ACD is accepted to be the most prevalent form of immunotoxicity found in humans (Kimber et al. 2002)[13]. By its allergic nature, this form of contact dermatitis is a hypersensitive reaction that is atypical within the population. The mechanisms by which these reactions occur are complex, with many levels of fine control. Their immunology centres around the interaction of immunoregulatory cytokines and discrete subpopulations of T lymphocytes.

ACD arises as a result of two essential stages: an induction phase, which primes and sensitizes the immune system for an allergic response, and an elicitation phase, in which this response is triggered (Kimble et al. 2002). As such, ACD is termed a Type IV delayed hypersensitivity reaction involving a cell-mediated allergic response. Contact allergens are essentially soluble haptens (low in molecular weight) and, as such, have the physico-chemical properties that allow them to cross the stratum corneum of the skin. They can only cause their response as part of a complete antigen, involving their association with epidermal proteins forming hapten-protein conjugates. This, in turn, requires them to be protein-reactive.

The conjugate formed is then recognized as a foreign body by the Langerhans cells (LCs) (and in some cases Dendritic cells (DCs)), which then internalize the protein; transport it via the lymphatic system to the regional lymph nodes; and present the antigen to T-lymphocytes. This process is controlled by cytokines and chemokines - with tumor necrosis factor alpha (TNF-α) and certain members of the interleukin family (1, 13 and 18) - and their action serves either to promote or to inhibit the mobilization and migration of these LCs. (Kimble et al. 2002) As the LCs are transported to the lymph nodes, they become differentiated and transform into DCs, which are immunostimulatory in nature.

Once within the lymph glands, the differentiated DCs present the allergenic epitope associated with the allergen to T lymphocytes. These T cells then divide and differentiate, clonally multiplying so that if the allergen is experienced again by the individual, these T cells will respond more quickly and more aggressively.

So, if I’m translating that into English correctly, proteins get involved and technically a hypersensitivity arises. It’s called an allergy because everyday English is loose with its terms and it’s a reaction that causes symptoms just like allergy does.

[sevenwood]

My wife is allergic to nickel. At least that’s the term we’ve always used to describe it. She gets a rash anywhere a piece of metal containing nickle maintains contact with her skin. She can’t ear a watch (even on expensive watches the backplate tends to contain nickle), and her gold jewelry has to be at least 14 carat (18 for “white gold”, which contains more nickle).

The term might be technically incorrect, but it seems to describe her situation fairly well.