RAST allergy test - Peanut Allergy Information

RAST allergy test

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I have heard that about 20% of the PA population outgrows PA. Does anyone know a person who has outgrown theirs? My 2 year old son had an huge reaction on skin test but the RAST was barely a class 3.

On Jun 27, 2006

Class III is actually pretty high for peanut allergy. I know of several people class II and lower who have had anaphylactic reactions.

From what I've read on all of DS's test results, the numbers used to determine class are the same accross the board - class 3 for egg is the same number range as class 3 for peanut, milk, etc. For some allergens the number can be higher with less likelyhood of being reactive and for some allergens the number can be very low and still have a high likelyhood of reaction. Studies have shown a 95% predictive value for certain allergens. These numbers mean that 95% of patients over a certan number (this varies for each allergen) will react to the allergen. There is also a lower number which 95% of patients below that number will not react. Results between the higher and lower number have around a 60% chance of reacting. I had a very old FAAN newsletter that had these numbers for several common allergens, but I have not been able to find the article either here at home or on FAAN's website . I do know that all of the numbers were lower than class III though.

Your child has the best chance of outgrowing the allergy by strict avoidance of peanuts. Also, having only a mild first reaction, no asthma, no eczema, no other food allergies also helps.

If you do a search of this site you will find stories of children who outgrew their PA. My DD outgrew her allergy; my DS and myself will not.

Welcome - Hopefully your child will be one of the lucky ones! Rebekah

On Jun 28, 2006

Hi, My son's RAST was very high for peanuts and Dr. Sampson told us he would probably not outgrow the allergy. His RAST for shellfish went up quite a bit. He told us not to freak out, that the RAST number does not predict how severe a reaction he might have. Very confusing to me. We just avoid all nuts and shellfish.

On Jun 28, 2006

Yes, exactly. The RAST number only predicts the likelyhood of a reaction not how severe a reaction will be.


On Jun 28, 2006

my husband claims to have outgrown a childhood peanut allergy, but i don't necessarily think he is certain he ever had PA specifically. he had many food allergies and sensitivities when he was younger, according to his mother. i have seen pictures of his skin when he was a very little boy - he was definitely reacting to something. oddly, he has no skin issues now and only had them as a very young boy.

he continues to be allergic to pecans and walnuts, but doesn't seem to react to peanuts (though we never have them in the home or eat them even when out). i do believe he has eaten peanuts as an adult on occasion, with no symptoms at all, before our PA girls were born.

so...it's difficult to say. he may or may not have been PA as a kid, but he seems not to have it now. at any rate, he has never had the severe reactions that our girls have had with their PA. my "gut" tells me he was never truly PA but was told he was allergic to nuts as a child and his family included peanuts in the nut family.

i could be wrong though. maybe he was in the lucky 20% (or whatever the number is).

On Jul 26, 2006

My nine year-old daughter has outgrown her egg, shellfish and finally her peanut allergy. She was diagnosed with her allergies after an asthma attack at age one. Over the years we have strictly avoided eggs, shellfish and peanuts and one-by-one she has outgrown them all. Two months ago she ate three peanut butter cups at Sick Kids Hospital in Toronto under the care of her pediatric allergist.

On Jul 26, 2006

that's awesome. i wish we had hope of outgrowing peanut allergy. (our rast results are due back next week....). we've retested the girls several times over the years and peanut always seems to go up, rather than down.

on the upside, our girls' other allergies (wheat, soy, egg) are now very mild (if not gone). they never caused anaphylaxis, even before though. we were lucky in that respect. only peanut is a "biggie" for us.

On Jul 26, 2006

Does anyone have anything in writing to explain the rast numbers and what they mean - stating that the rast number only predicts the likelihood of a reaction and not how severe it will be? I have the info explaining the different classes and what numbers fall into which range but nothing that states anything regarding how it relates to reactions. This has always been confusing to me and I probably don't do a very good job of trying to explain it to others. Something in writing would help. Thanks!

On Jul 26, 2006

There is no correlation between score and reaction

You can go into anaphylaxis from an allergen of score .35 (or negative, even!) or a score of >100.

Whats it all mean? Use the testing as a guide... If positive, avoid. If the score goes down to a low level, then challenge (with docs ok). If pass challenge, talk to doc... Tests are NOT 100% accurate.


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