As allergists, we must not only be expert in our requisite field of technical immunological knowledge, but also in applying it in the context of the patient whom we carefully observe and listen to.   It is the fusion of expert technical knowledge and expert practical observational and listeniing skills that makes us expert allergy clinicians.  It's been my experience that certain signs seen in day-to-day allergy practice haven't been given enough emphasis, or reported in the literature.  It was in this spirit that (In my last post), I had discussed what I had termed "Eaton's Sign"--the curious phenomenon of "recall" activity at prior skin test sites  when an allergy patient subsequently is re-exposed to his/her allergen.  But wait!  There's more!  In a sense, Eaton's sign is part of a bigger picture--the allergic "target organ" phenomenon.  Here's the story:

When an allergy patient is exposed to an allergen (either by inhaling it or ingesting it), he/she may be principally/preferentially affected at a sight of prior trauma.  The site of prior trauma may be accidental (an injury or infection) or deliberate (a prior surgery).   Here are some examples:

  Case 1:  A patient comes to see me.  He was aware that previously he would ingest milk and have problems with immediate sinus congestion and posterior nasal drainage.  Then he had a car accident and suffered serious whiplash.  Now when he ingests milk, he develops not only sinus congestion and drainage, but his neck aches terribly...

Case 2:  A patient comes to see me with episodic urticaria and pruritis.  When she ingests the wrong food or breathes an allergen, the first site that reacts is a small area on her abdomen....on exam, this is the exact site of a surgical scar where she had a laparoscopy years earlier.

Case 3:  A patient comes to see me.  He states that he is seeing me for knee pain.  He has been scoped three times previously, and only old, degenerative knee disease is seen.  Nothing new.  His orthopedist is mystified that the patient has more kinee pain in the fall season, precisely when he has more sinus and mucous drainage.

Case 4: A patient comes to see me, with a history of a prior scabies episode adequately treated.  But she continues to suffer from periodic episodes of intense pruritis at former sites of infection.  When her corn allergy is diagnosed and treated, the residual pruritis resolves.   

As might be expected, the permutations on this principle are endless.  Among others, sites of prior herpes zoster are particularly vulnerable to subsequent allergic reactions. In short, sites of prior trauma--whether accidental, surgical, or infectious--are all fertile areas for subsequent allergic reactions.  Presumably, cytokine release during allergy reactions preferentially "targets" these vulnerable areas that have preexisting prior trauma, damage, and residual inflammation.  

In short, as good allergy clinicians, we must keep our "eye on the target" at all times.  

Later, Dude