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Allergies Can Be So Specific That a Person Can React to a Egg's Yolk But Not Its Whites

Food allergies can be quite specific, triggered by a single species rather than entire genre such as "seafood"

Just because you're allergic to one food stuff, like Nile perch, doesn't mean you're allergic to every fish in the sea (or lake or stream or river or pond). New research finds further evidence that food allergies can be quite specific, triggered by a single species rather than entire genre such as "seafood." In some cases, other studies found, selecting only certain components of a single food—egg yolk but not egg white, for example—can mean the difference between enjoying a Sunday morning omelette or breaking out in an allergic reaction.

Outside Online expands on this subject:

To determine which parts of a food are fine to eat and which parts will actually cause a reaction, allergists perform oral food challenges. These involve feeding a patient tiny amounts of the suspected allergenic food in increasing doses.

Allergist Joyce C. Rabbat confirms, writing, "Certain proteins of a food are more allergenic (i.e., more likely to cause an allergic reaction) than other proteins of the same food."


Detailed biochemical analyses can also shed light on specific allergy triggers.  In Europe, researchers explored the line between allergic and not by recruiting two dozen people with a confirmed allergy to Nile perch. Their studied was inspired by a Norwegian chef who had suddenly developed an allergy to Nile perch after consuming salmon (researchers call this a "cross allergy," or antibodies produced in reaction to one food that suddenly begin to react with a different but similar food), but did not have any problems with other fish, like cod. They paired serums, which contain antibodies, from the test subjects with various proteins extracted from the fish to see which components exactly triggered their allergic reactions. They found that not everyone experienced an allergic reaction to both perch and cod, although conventional allergy tests likely would have indicated those patients were allergic to fish as a whole. 

"The tests that are currently used are very non-specific," the researchers concluded. "For some people who suffer from fish allergies there may be hope of finding a fish that they can tolerate if we managed to make the relevant tests suitable for mass implementation and use them in allergy diagnostics."

More from Smithsonian.com:

Bullies Are Now Using Their Victims' Allergies Against Them 
Tick Bites Cause Freak Allergy to Meat-Eating 

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