RAST question for someone never exposed to peanuts

Posted on: Wed, 07/12/2006 - 10:54am
SallyL's picture
Joined: 02/20/2006 - 09:00

I thought I'd read here that if someone was never exposed to peanuts then the RAST test would be inaccurate. Is that true? My DD has only been exposed through prick tests, never through consumption. Do you think the RAST would still be accurate? I can't find anything about it either way. Thanks!

Posted on: Wed, 07/12/2006 - 11:09am
Precious1971's picture
Joined: 12/21/2005 - 09:00

Quote:Originally posted by SallyL:
[b]I thought I'd read here that if someone was never exposed to peanuts then the RAST test would be inaccurate. Is that true? My DD has only been exposed through prick tests, never through consumption. Do you think the RAST would still be accurate? I can't find anything about it either way. Thanks![/b]
I, too, searched for information on this as well. Unfortunately, there are no "non" exposure to peanuts. Peanuts are everywhere.
According to the book by Scott Sicherer, M.D. "The Complete Peanut Allergy Handbook", you can avoid peanuts with all your might (even if you never had eaten a peanut in your life) and still can be allergic. He also adds that type is extremely rare.
In my case, even though I'd eaten peanuts all of my life until I was tested positive on the Scratch Test, I avoided them. I decided to get another opinion--this time, with a RAST test (blood), I was <0 on on the top 8 food allergens and including all nuts. I still avoided nuts then until my dad decided to BOIL peanuts for 4 hours, I had a topical skin (very annoying skin reaction) three hours later.
The doctor I saw, said that was extremely rare for me to "break out" in three hours...when the norm is within minutes to an hour. So, it is been a guess that I had delayed reactions.
Everyone is different with reactions and severity of them as well.
[This message has been edited by Precious1971 (edited July 12, 2006).]

Posted on: Wed, 07/12/2006 - 11:15am
alliedhealth's picture
Joined: 06/10/2006 - 09:00

My understanding is that you have to be sensitized via exposure before the tests would be accurate. Our allergist has indicated that ImmunoCap testing our 10 month old at this point (sibling of PA brother) would not be necessary as she has never been exposed to peanuts while I was pregnant, or during nursing, or through our diet.
I did read somewhere about immediate reaction to peanuts this first time a child was ever knowingly exposed- they were not sure whether the child had been exposed to traces or what- it may be in [url="http://www.allerg.qc.ca/peanutallergy.htm"]http://www.allerg.qc.ca/peanutallergy.htm[/url]
Many allergists feel that testing on siblings should only be done with evidence of atopy/ eczema or clinical history rather than just random testing. I would not be sure if SPT would be enough exposure for a positive RAST.
AS always my disclaimer [img]http://uumor.pair.com/nutalle2/peanutallergy/smile.gif[/img]
I would consult a board certified allergist with specialty in food allergies for better info

Posted on: Wed, 07/12/2006 - 11:22am
alliedhealth's picture
Joined: 06/10/2006 - 09:00

The article I quoted does discuss SPT and lab results in "peanut naive" children. You can find the section by searching for "naive" in the document or looking under diagnosis of food allergies

Posted on: Wed, 07/12/2006 - 12:19pm
starlight's picture
Joined: 01/16/2004 - 09:00

Doesn't the skin prick test count as an exposure?

Posted on: Thu, 07/13/2006 - 3:50am
SallyL's picture
Joined: 02/20/2006 - 09:00

I wasn't sure if the skin test counted as an exposure...that was part of what I was curious about. She's never consumed it...not knowingly. She was diagnosed at 18 months and I hadn't planned to let her have nuts until 2 or 3 years old.
She may have been exposed while I was pregnant and nursing I suppose. I spoke to a number of nurses and doctors who all okayed peanuts during nursing and pregnancy. Ironic that I was so careful about allergies (or so I thought) and here she is allergic...yet my friends give pb to their 12 month olds and no allergies. Argh!

Posted on: Thu, 07/13/2006 - 4:24am
gw_mom3's picture
Joined: 02/14/2000 - 09:00

According to our allergist, SPT does not count as an exposure. Another allergist gave our younger two (nka) cap rast tests a few years ago, and then after it was all done said they probably wouldn't be accurate since they both had never been directly exposed. I would have preferred to know before we stuck the kids and shelled out the $$.
We'll probably be getting the younger two skin tested before too long. I'd like to know for sure one way or the other.

Posted on: Sat, 07/15/2006 - 3:10am
anonymous's picture
Joined: 05/28/2009 - 16:42

Exposure through cross-contamination is enough exposure to trigger a positive RAST test or skin test. That's how my child ended up testing positive at 17 months. We had never fed him peanuts, but hwe ate in restaurants that had peanuts on the menu and thus may have had cross-contamination in his food, and we fed him products that we later discovered have warnings for may contain traces of peanuts.

Posted on: Thu, 07/20/2006 - 12:32am
jtolpin's picture
Joined: 05/28/2003 - 09:00

I dont buy it.
Caitlin RAST + to nuts and peanuts.
She RAST + to lobster, shrimp, crab too.
Ann, while PG, NEVER consumed them. NEVER. (she's anaphylactic).
Ann, while, BF'ing, never consumed. (see above)
Caitlin enver ate them knowingly. Sure, maybe SOMETHING was xcontam with peanuts, or nut, maybe two... of them? No.
But in reality -- NOTHING she ate contained lobster, shrimp, crab... EVER. No chinese food for her.. no NOTHING.
I firmly believe you CAN test positive to stuff 'just because'.
Just my UNMEDICAL based opinion.
(BTW: We're back from Myrtle Beach) [img]http://uumor.pair.com/nutalle2/peanutallergy/smile.gif[/img]
[b]* Obsessed * [/b]

Posted on: Thu, 07/20/2006 - 1:52am
luvmyboys's picture
Joined: 05/25/2006 - 09:00

edited to delete double post - luvmyboys
[This message has been edited by luvmyboys (edited July 20, 2006).]

Posted on: Thu, 07/20/2006 - 1:53am
luvmyboys's picture
Joined: 05/25/2006 - 09:00

I think the point is, you could be unaware of exposure and still test positive AND you could also test negative now, but due to inadequate exposure perhaps(?) test positive later. DS#2 tested negative at 2.5 years old via RAST and at 4.5 tested class 3 for PA and 4 for Walnut despite no rxn or known exposure. WHY? The only exposure I am aware of was when I was BF'ing before 6 months old. He eats a subset of what ds#1 eats. DS#1 is anaphylactic to pnut and had no known rxn so it had to be residue or slight cross-contamination that triggered the positive RAST results I guess...or it just happened for no reason!


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