A Brief Explanation of Allergies

Something has been bothering me for a while.  Why, if I’m allergic to nickel, can’t I simply take an antihistamine to stop the allergic reaction?  I have friend who is allergic to bees, and a good dose of Benadryl fixes everything.  Why won’t that work for me?

The answer, apparently, lies in understanding the different types of allergens.

An allergy is a type of medical condition called a Hypersensitivity.  Hypersensitivity refers to “undesirable reactions produced by the normal immune system.” [1]  These hypersensitivities are classified into five different types.  Type I is a standard allergy with an immediate response.  For example, my friend is stung by a bee, and she immediately breaks out into hives.  Nickel is a Type IV hypersensitivity.  Type IV is also known as delayed-type hypersensitivity.  This means that contact with the allergen causes a delayed reaction.  For example, I come into contact with nickel, and as many as three days later, I may develop a rash.

Without getting too technical (or falsely pretending I remember that much from college biology) – the difference between the two types is as follows: 

Type I reactions involve antigens and antibodies.  When your body is exposed to the allergen, it creates antibodies, these antibodies then recognize the next time you’re exposed to the allergen, and order the release of histamines, leukotrienes, and prostaglandins, etc.  These cause the symptoms we most often associate with allergies – stuffy nose, watery eyes, hives, swollen throat, or anaphylaxic shock.  These types of reactions are treated, therefore, with anti-histamine, epinephrine, or corticosteroids.

Type IV reactions do not involve antibodies.  Instead, the reaction happens on a cellular level.  “Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of phagocytes, natural killer cells (NK), antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen”.[2]   In very layman’s terms – when your body recognizes the allergen, those cells send out an SOS signal, and other cells show up to remove or kill the allergen.  They’re like a cell black ops – these are the tough guys who come in and do whatever it takes to get rid of the allergen.   Type IV reactions are an allergy, but it's more of a rejection of something that doesn't belong.  This is the same type of reaction your body has to cancer cells or when a transplant is rejected.

Hindsite is 20/20.  When I was badly sick from the nickel in the braces, I felt like I was being poisoned.  My body didn’t LIKE something, and it was trying to get rid of it.  I never knew that that was the definition of a type of allergic reaction.  I find it astounding that I used that analogy back then, not knowing any of this at the time.  Our bodies are smarter than our brains!  I do wish I had listened to mine better.

So understanding a little more about two of the types of allergies explains why a nickel allergy can’t be treated like other “common” allergies.  (I put common in quotes there, because nickel is now listed as the top allergen in the world).  Anti-histamines don’t work, because your body isn’t reacting by releasing histamines.  Your cells themselves are on red-alert trying to kill the intruder.  Unfortunately the only fix I know so far is to remove the culprit (nickel), and let your body heal from the damage.

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[1]  (http://en.wikipedia.org/wiki/Hypersensitivity)

[2] (http://en.wikipedia.org/wiki/Cell-mediated_immunity)