Egg skin test

[Erica]

I am brand new to this forum and have tried to search for the answer to my question but haven't found it. My two year old son has tested positive for milk, egg, peanut and tree nut allergies through skin prick test. My question is- his score was a 4+ for egg last year and this year it was a 3.  Does this indicate that he is beginning the process of outgrowing his allergy? Is a blood test more accurate? thank you in advance for any replies.

[CMdeux]

Hi, Erica.


I'm not sure that there is a super-clear answer to your question-- I'm sorry about that.  Neither skin nor blood tests are all that accurate, sad to say. 

Can I ask what prompted skin testing initially? 

The preschool years is when some children do outgrow milk and egg allergies in particular-- but I don't want to raise your hopes, either, if you've seen reactions to either thing-- particularly severe reactions to them.  The fact is, something seems to have changed in atopic children born after about 1997-1999-- those children outgrow "childhood" food allergies VERY much later than used to be conventional wisdom. 

My daughter was in that group-- and she hasn't truly "outgrown" her own egg allergy at nearly 18, she's just got a high enough tolerance that she isn't at risk of anaphylaxis from accidental exposures, and tolerates COOKED egg almost as though she didn't have the allergy.    Her milk allergy didn't play by the rulebook, either. 

But at 10, she was still very definitely highly allergic. 



So-- if you HAVEN'T ever seen any reactions to those foods, then I'd look for an allergist that will schedule some food challenges, or at least discuss additional blood testing and then see if challenges are the right thing to do.  It's a LOT better for kids to not be encumbered by this lifestyle once they enter school, if you can possibly avoid it by then.  (Of course, it's not the end of the world if you can't-- we've all done it, obviously). 

Just noting that skin testing (RAST blood testing) alone-- without clear allergic reactions-- is NOT considered a good diagnostic standard at this point, simply because so many people will test positive even though they tolerate ingestion of the food just fine.    Of all positive skin tests to foods-- only about 50% are in people with notable clinical reactions to the food.  Similarly with blood testing (though it's not always the same 50%). 

There IS a positive predictive value in the relative SIZE or response in skin prick tests, though, and certainly a high RAST value means a high likelihood of clinical allergy-- so a skin test that took over an arm, or half of a child's back.... yeah-- that's probably not worth challenging.... but one which is about the size of the histamine (+) control prick, that might be worth thinking about, in the absence of clear reaction history to the food.

I really hope that something in there is helpful.  I know that it's so hard to have hope, retest, and feel that nothing has changed.   

[krasota]

Egg, in particular, can provoke skin reactions when it doesn't necessarily provoke ingestion reactions, through some wacky immune thing that I don't fully understand, but have experienced with my own son, who now tolerates baked egg, reacts to some egg on contact, and has a positive skin test (can't remember what classification, but bigger than a nickel). 

I'd definitely ask about challenges.  Or do bloodwork so you have comparisons in egg-specific IgE from year to year.

[Mckenny]

I didn't know that was possible. I would have thought that ingesting something would cause a bigger reaction that getting it on your skin every time. Is this a known thing with egg allergies?

[Paiyada]

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