Janice couldn't be happier at the restaurant.  Everything was as it should be--the atmosphere was nice and the food was perfect. Because of food allergies, she tried to keep her diet simple when eating out--generally nothing exotic, just a fine steak and a baked potato.  She had eaten at this restaurant before and usually had the same meal--and it worked.  Good food.  No allergy reaction.  A great combination.  But this time it was different:

The entire inside of her mouth started to itch.  Badly.  

Janice had a long list of food sensitivities--wheat gave her malaise and aching, and milk gave her nasal and sinus congestion.  But only one product caused her mouth itch:

Carrageenan.  

Carageenans belong to a group of polysaccharides extracted from red seaweed.  Commercially they are used as an emulsifier and  thickener in the food industry.  And it can cause allergic reactions.  It's even been responsible for anaphylaxis in barium enema solutions.   

WIth some prior detective work, we had discovered the source of Janice's chronic mouth itching, and after Janice changed her toothpaste, and avoided items with carrageenan, she was fine

Until now.  

She looked down at her meal.  The same meal she had eaten at the restaurant a week before.  On top of the potato was sour cream--on a hunch, she asked the waiter,

"Did you change your brand of sour cream, and does it have an additive in it called carrageenan?" she asked.  After a dumbfounded look, the waiter agreed to check.  And he came back to her table with the answer:

Yes, and...yes.

Janice had known she had a unique reaction to carrageenan--what I call an "allergic fingerprint."  Her symptoms were so characteristic of contact with this item, that even in the absence of observing the she was eating something with it, she knew she had.  Just like a detective who can dust for fingerprints and determine that so-and-so was at the scene of the crime, even tho the detective had never seen the criminal there himself.  

As I've worked with patients over the years, I've been intrigued with the phenomenon of "allergic targeting"--i.e., a person can be blood-test  positive to 3 foods, but the symptoms each food elicit may be completely different--i.e., like Janice's case with wheat, egg, and carrageenan each affecting different target organs.   "Allergic fingerprinting" can often be the result of these discoveries, and this, in turn,  can help the patient be their own detective.  

In another situation I recall a husband telling me he would buy his allergic wife the same organic flatbread that had calcium proprionate and NO sodium metabisulfite in it, since she was quite sensitive to sulfites.  One day he bought the usual "safe" flatbread at the store.  His wife prepared the meal with it, and as she ate it she started to cough and itch. 

"What brand did you buy" she asked.

"The same as usual" he said. "The one without sulfite--they use calcium proprionate in it instead."

"Well, I don't care if it is the same brand, it has sulfite in it," she exclaimed.

So the husband rummaged through the garbage, found the wrapper, and upon reading it he discovered they had changed from calcium proprionate to sulfite as the preservative!  

There is an important corollary for this story--all allergic patients must re-read the label of every item they pick up at the store.  Just because you are buying the same named product doesn't mean the ingredients haven't changed.  The wife's certainty she had discovered an "allergic fingerprint" led to the realization by the husband that (surprise!) labels (and ingredients) can change. And these ideas even carry over to medications and vitamins that a person takes.  Consequently, an attitude of vigilance is needed for every allergy patient.

"Allergic fingerprints".  Something to think about.  And an invaluable tool for the Allergy Detective.  

Later, Dude