Testing for food allergies - Mothering Forums
 
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#1 of 16 Old 10-25-2007, 06:20 PM - Thread Starter
 
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I'm wondering what the most accurate method for food allergies is.

When I had testing, they did the skin test (for both food and environmental).

For my 4 yr old, the pediatrician said that the blood test is more accurate when testing for food allergies.

Wondering if that's true and if I should get my blood tested to see if it matches the skin tests.

Thanks.

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#2 of 16 Old 10-25-2007, 06:29 PM
 
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Well, this is going to be kind of unhelpful, but we've done both skin and blood multiple times for my son and didn't get great results. We still haven't found all his allergies. It's really frustrating to get all hopeful over getting some answers and never really getting any. I hope you have better luck than we have!
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#3 of 16 Old 10-25-2007, 06:35 PM
 
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My dd's doc does skin testing followed by blood testing. So while her skin testing didn't show peanut (which we KNOW she's allergic to because she has gotten hives the 2 times she had it) it did show on her blood test. She also was skin + to soy, but - by blood. I've noticed with soy, she simply goes crazy if she eats it and her eczema flares with high quantities.

So, IMO both are needed to get a true list of allergens (and even then, not all will show up unfortunatly.)

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#4 of 16 Old 10-25-2007, 06:48 PM
 
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I have had skin and blood testing and the blood tests showed more than the skin prick tests.


With kids, it can be hard to say...younger children might not have built up enough histamines to things so they might not show up as "allergic" on tests.

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#5 of 16 Old 10-25-2007, 07:03 PM
 
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We did the blood test (RAST) when DD was 12 months.

At first I thought it was totally wrong. It only showed corn and strawberries. But she had been reacting to tomato sauce so I was sure she had a tomato allergy.

Turns out there was corn syrup in the sauce I used. Now I know not to buy anything with corn syrup in it.

So yes, I think the blood test is accurate.
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#6 of 16 Old 10-25-2007, 07:42 PM - Thread Starter
 
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I just wish that the doc ordered more things to be tested for. Because I'm allergic to many foods, I wanted my child tested for those to start with. But he's only doing shellfish (or maybe just shrimp, even though I told him to do it for shellfish), and almonds. I hope they test for a bunch of the nuts though.

Getting blood from my child is not a pleasant experience and would not want to do that again any time soon. Poor thing.

Thanks for all the replies so far.

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#7 of 16 Old 10-25-2007, 08:15 PM
 
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Quote:
Originally Posted by DaughterOfKali View Post
I just wish that the doc ordered more things to be tested for. Because I'm allergic to many foods, I wanted my child tested for those to start with. But he's only doing shellfish (or maybe just shrimp, even though I told him to do it for shellfish), and almonds. I hope they test for a bunch of the nuts though.

Getting blood from my child is not a pleasant experience and would not want to do that again any time soon. Poor thing.

Thanks for all the replies so far.
He only did shellfish and almonds?!?!?!?!

I would ask him to do more than that

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#8 of 16 Old 10-26-2007, 03:54 PM - Thread Starter
 
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Yep, I told him that I wanted testing for everything that I'm allergic to (and told him what they are) but when I heard the techs talking, I think they said they were only testing for 2 or 3 things. argh.

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#9 of 16 Old 10-26-2007, 04:14 PM
 
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We've done some of both. We did the blood test, but it was for a MASSIVE panel of things. They did one draw and tested her for: fish, shellfish, dairy, soy, peanuts, rice, wheat, cockroach, cat, dog (these were environmental, not food!), almonds, brazil nuts, cashews, pistachio, sesame seeds, walnuts, pecans, eggs...a few more things I can't remember.

We did one set of scratch tests, for about 5 things. I found it a little...fuzzy. Dd actually reacted to the negative control; they did it twice, once with a brand new bottle of stuff, to make sure it wasn't a contamination issue...apparently, she has sensitive skin. She came back completely negative to soy via skin prick (it was smaller than her negative control) and had very low numbers on her RAST, but seemed to have a very, very mild reaction--a bit of diaper rash--when we trialed it after the scratch test. So, in that case, I think the RAST was more accurate. For things to which a child is highly allergic, I think skin test is fine--dd's scratch for rye blew up, and since we know she has a severe wheat allergy, that made sense. For more borderline things, I think it can be hard to interpret.

We'll do the blood testing again next summer (a year later) and I plan to throw in everything and the kitchen sink: all her allergens, plus some common things for which she hasn't been tested (like chocolate) and hasn't had or has had very mild reaction to (like tomatoes). If they're doing the draw, they should test for as much as humanly possibly.

If you suspect allergies in your daughter, I wouldn't limit it just to the foods you're allergic to--the propensity for allergies is hereditary, but the specific allergies are not (thus many people with seasonal allergies, like my dh, have food allergic children). You're the consumer. Your doctor works for you. Insist on the tests you want or fire him. FYI, they usually keep the blood for a few days and you can order more tests after the original round--we didn't initially test dd for tree nuts, but when she came back + for peanuts, my doctor called the lab and had them run all the other nuts with the sample they already had.

From what I've heard, positive results on the blood draw are around 50% accurate, negative results are about 90% accurate. So it's definitely not ideal, but as you do more tests over time and likely have a set of real-world reactions to go off, you can get a decent picture.
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#10 of 16 Old 10-26-2007, 04:15 PM
 
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Just because you are allergic to a certain food does not mean your dd will also be allergic to that certain food. It increases her overall likelihood of having allergies. Neither of my children have ever been tested for food allergies as they only test for one kind of reaction. I'm not so good at explaining the difference, but you can be allergic to food or any other item and not show up as allergic on those tests. That's why I've never put my children through them. Thankfully the NP my children see trusts me and when I said ds is very allergic to eggs she went to get a huge orange sticker to put on his chart. His reaction to eggs likely would show up on those tests as he broke out in hives, but I still don't trust them.

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#11 of 16 Old 10-26-2007, 04:48 PM - Thread Starter
 
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I know that my specific allergies may not show up in my little one but, so far, it seems to be heading that way. That's why I wanted to include all the ones that I'm allergic to.

We tested long ago for milk, soy, eggs, gluten but they were all negative.

That stinks that a positive result is only 50% accurate!

I would call the pediatrician to have more things tested but he's not working today.

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#12 of 16 Old 10-26-2007, 05:29 PM
 
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I've heard blood tests can show more stuff. I had a skin prick test done and I picked up on reactions the dr. didn't. He said I was only allergic to filberts. I went with whatever was itchy - apples, milk, eggs, peas, filberts, almonds, shellfish. When I took milk out of my diet (stopped drinking it straight each day with meals), the daily headaches went away. I'm seriously allergic to anything with a pit (peaches, plums, nectarines, cherries) and that didn't come up.

So if I had listened to just what the doc said, I'd still be having headaches everyday and would be thinking it was normal for my throat to close up after eating pitted/seeded fruit!

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#13 of 16 Old 10-26-2007, 07:23 PM
 
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Here are some links to previous threads discussing allergy testing:

https://www.mothering.com/discussions...d.php?t=718876
https://www.mothering.com/discussions...d.php?t=742947

My dd had the skin PRICK test and the RAST. She is supposedly negative for everything and yet her eczema rages on. : They can only test a few foods with the RAST at one time because it requires so much blood (they use the serum). But your doc should have ordered a few more than two foods because they can draw enough blood for at least 7.

Apparently most allergy testing has a high incidence of false positives. But I still think that it's a good place to start. Even if your dc isn't allergic to something that shows up on the test, you can find out by challenging it!

There are two other tests out there: the skin PATCH test and the IgG/IgE blood test. These two test for the delayed allergic reaction (non IgE mediated responses), unlike the prick and RAST, which tests only the IgE response. Both these tests can test for many allergens (over 100 in the case of the blood test because it uses ELISA). Neither of these tests are approved by the board of pediatrics so a board certified doc is unlikely to do them. You may have to search or in the case of the blood test, you can do it yourself out of pocket. According to clincial studies I have read, the patch test is very accurate and very specific (we're talking in the 90th percentile for infants and children), it simply has not been standardized yet. The blood test also has not been standardized and the clinical studies that looked at the IgG response are not conclusive regarding accuracy and specificity. You can read the posts by other mamas that have pursued this route to see some success and some disappointment.

HTH!

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#14 of 16 Old 10-26-2007, 08:40 PM
 
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Originally Posted by Jaimee View Post
They can only test a few foods with the RAST at one time because it requires so much blood (they use the serum). But your doc should have ordered a few more than two foods because they can draw enough blood for at least 7.
I don't think this is correct. They tested about 15 things for my dd with one blood draw when she was 13 mos. Unless they did a different kind of test? But I'm fairly certain it was RAST...
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#15 of 16 Old 10-27-2007, 12:21 AM
 
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Originally Posted by NYCVeg View Post
I don't think this is correct. They tested about 15 things for my dd with one blood draw when she was 13 mos. Unless they did a different kind of test? But I'm fairly certain it was RAST...
It's possible that they can draw more blood from a 13 month old than they could from my 8 month dd. Since the op's dc is 4 years old, perhaps they could test even more, but certainly not 50-100 like they can with ELISA or the patch test.

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#16 of 16 Old 10-27-2007, 03:52 PM - Thread Starter
 
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Thanks everyone!

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