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 Post subject: Skin test v. blood test
PostPosted: Mon Aug 22, 2011 8:31 pm 
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Joined: Sat Aug 20, 2011 4:06 pm
Posts: 9
Location: USA
I'm getting blood drawn soon for allergy testing (general food allergy pannel, since I have year round allergies, eczema, and have 2 relatives with PN/TA allergy). I've seen a lot of people come back confused, not sure what to make of the results. Is there a such thing as false positives, and false negatives? Because honestly? If I don't test positive for peanut allergy, the first thing I eat will probably have peanut or peanut butter in it. (Same with if I don't test positive for kiwi.) and I don't want to end up finding out the test was wrong the hard way.

Everyone tells me the blood test is more reliable, but other people INSIST I need to do the skin test to be absolutely sure.


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PostPosted: Mon Aug 22, 2011 9:05 pm 
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Joined: Mon Feb 07, 2005 6:39 pm
Posts: 2925
Location: Toronto
Salma, The first question any allergist would ask you is: have been having any symptoms that look like an allergic reaction? You mention peanut butter - if you're eating it right now without symptoms - stomach ache or vomiting or hives - not too likely you're allergic to it. (Trust me, you'd know!)

The "history" of incidents when eating a food is considered almost important as the test. Both the skin-prick test and blood test are useful tools but, yes, there can be false positives.

If you did get a positive and there was suspicion you might not be allergic, an allergist can do an "oral food challenge" - you eat a little bit of a food, then a little more. If no symptoms, you pass you're not allergic. It's considered the gold standard of tests. But you can't do it in a lot of people who may well be allergic.

Here's a good writeup Allergic Living has on the tests: http://allergicliving.com/index.php/201 ... allergies/

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Allergic to soy, peanut, shellfish, penicillin


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PostPosted: Mon Aug 22, 2011 9:06 pm 
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Joined: Mon Sep 05, 2005 12:53 am
Posts: 373
Location: Alberta
What do you mean by a "food panel"? We've only ever been tested for the specific foods that we have suspected. There are IgG blood tests out there that will test for 90+ foods, and those are essentially bogus. You can usually spot these because they are offered by private labs / naturopaths etc, and they have to be paid for out of your own pocket. I remember reading an article where someone had several of these food panels done, and they came back with a different list each time. So yes, those tests are not only confusing, but are completely unreliable. I looked into these years ago because a local lab tried to sign me up as a provider ... they basically sent me a marketing package, showing me how much money I could make charging my patients hundreds of dollars for private laboratory testing! Saliva, hair, you name it .... didn't take long for me to discover that these were all very unreliable types of testing, and cause patients to avoid foods unnecessarily, or take un-necessary supplements to correct deficiencies that don't really exist. It is a huge problem right now, and there's nothing much that can be done about it. (Ever heard the term "Adrenal Fatigue"? Doesn't exist. It's a made-up diagnosis, and the latest fad.)

The IgE blood tests are the ones that are used by allergists, and they cannot diagnose food allergy by themselves. The results of the IgE tests, combined with skin test results and history of reactions are the usual method of diagnosis. We have never had to pay for these blood tests, but skin tests are not covered in our province, so those are a flat $40 fee. It's been the same for almost 10 years of doing it, through 4 different allergists.

I recently followed some links onto the Allergic Living website, and found an excellent review of allergy testing. You can find it here :

http://allergicliving.com/index.php/2010/09/03/testing-for-food-allergies/?page=1

Good luck!


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PostPosted: Mon Aug 22, 2011 9:16 pm 
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Joined: Sat Aug 20, 2011 4:06 pm
Posts: 9
Location: USA
gwentheeditor,

Yes (hives around the mouth), but I don't know what to, exactly. It could be kiwi, it could be strawberry, or peanutbutter--it could be something entirely different. Or none of the above. I never really liked peanut butter in the first place, but after I had to cut it out completely, I'm so tired of checking labels, and I actually kind of miss PB toast. The other thing is, I have a lot of IBS-like symptoms, so between those, my allergies, eczema and other things, I really want this test done to try and figure out what's going on.

It's a long story, but I've got SOMETHING going on, and we're just trying to cover all the bases.


Momtobunches,

My doctor told me they could do a panel, and test me for the top allergens, and any others I asked about. I had blood drawn a while ago and sent off to be tested, but they didn't take enough blood, so I have to go back and give more. That's definitely not encouraging, and actually a little scary to hear...I had been hearing the exact opposite. I'd believe it, though. Honestly, I would.

I was also wondering why so MANY people left with confusing results and had to come on line to ask about them and how to interpret them...that's really sad.

And yes I've heard of "adrenal fatigue." Doesn't surprise me, either. *shakes head*

Thank you both for the links, I will look into them.

Update: I just went and had blood drawn this morning. Curious to see what the results are, but I am also going to ask about trying another test like the skin test or the food challenge.


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PostPosted: Sat Oct 15, 2011 4:02 am 
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Joined: Fri Sep 16, 2011 7:49 am
Posts: 36
Location: Toronto
My current allergist, who I totally respect said to me that blood/skin test doesn't mean if things don't show up you may still react.

The honest and best method of allergy test is keeping a detailed food log. Write what you ate and what was in it.

Sometimes skin/blood tests don't show up but you can still be allergic to specific food items.

If you react on a regular basis to blank food, but no blood/skin tests show it, chances are you ARE allergic to it.

It seems like common sense but again my allergist says some tests show negative BUT you just have to keep track of your own body. That is sometimes better than blood/skin tests.

Trust your own instincts/history.

Hope this helps.


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PostPosted: Tue Oct 25, 2011 5:11 pm 
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Joined: Fri Sep 16, 2011 7:49 am
Posts: 36
Location: Toronto
I will say one last thing on this subject.

I did blood tests and skin tests. I found and the nurse who did my skin tests more stuff showed up. In fact when I did blood tests NOTHING showed up yet when I did skin tests some things showed up.

The trouble with me is unless I fast for 4 days straight, which isn't happening, I almost always react to something every 2 to 4 days and having antihistamines, i.e. Benedryll 4 days or less decreases the chances of things showing up, or things might show up but the reaction might be a lot milder.

For example I brought an apple and my skin broke out in hives yet normally if I don't have antihistamines in my body then my lips swell up, hives and sometimes even go into anaphylactic shock.

Just saying.


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