How sensitive?


My 5 month old son was tested positive for peanut allergy. I understand this is considered a lifetime allergy. How accurate are tests for determining the severity of his allergy? Does anyone know of someone who outgrew this allergy?. Hope to hear from someone on this topic.

On Mar 31, 1999

Hi Dee!

What type of testing was done? Was it just a skin prick? Or was it a blood test? In order to have the best blood test, your allergist should do a CAP rast test (CAP System Quantitative Antibody Flourscein-enzyme Immunoassay (FEIA) Pharmacia & Upjohn Diagnostics, Uppsala Sweden. This is not the typical blood test done for allergy. The CAP rast measures kUa/l's per liter. According to Dr. Hugh Sampson (Mt. Sinai), for peanut, the diagnostic level of IgE can predict clinical reactivity with greater than 95% certainty. So, if the result is 15 or greater, your child will be QUITE reactive to peanut.

This stuff all was relevant to our situation when our allergist suggested our son have a peanut challenge - based on a study by Hourihane et. al. Our son is allergic on skin test and conventional blood allergy testing, but has no know history of ever ingesting peanut. I do believe, however, he has had one airborne reaction. I spoke with Dr. Sampson about this -- the CAP rast is the only Rast which can give you a fairly accurate indication of what would happen if your child ate a peanut. I don't think the test is used standardly by allergists yet - we had to search high and low in our area for a blood lab that even knew what it was, or where to send it. Dr. Sampson is "the" peanut allergy authority - get the test done!

By the way, ultimately, we did not do the challenge. My son scored a 6 on the CAP rast --i.e. moderate food specific allergen. The Hourihane study has been bashed by others in the medical field (the children the study claimed "outgrew" the peanut allergy were never proven to be allergic in the first place. Plus, the numbers 2 out of 62 outgrowing the allergy did not impress me). Finally, I believe my son has had a second airborne reaction since the time of his CAP rast. Hope this helps!

[This message has been edited by LauraP (edited March 31, 1999).]

On Apr 1, 1999

We had our son skin tested at 15 months of age after a reaction of about 8 hives. He tested 2+ positive on the skin test. Soon after that we believe he had a reaction of hives after being five feet away from an open jar of peanut butter (however he had been playing with the dog 30 minutes earlier and he is allergic to them also). The allergist was thinking we should sort out if he does react to airborne exposure by opening a jar of peanut butter in the office. Of course the idea of this scared me to death. I asked her if we could have the CAP RAST test done and if it came back low then I might consider it. Well, the CAP RAST came back negative! I got my hopes up really high til I read about possible false neg results. The allergist decided to do a skin test because they put more stock in those results. For the first ten minutes it didn't look like it would react but by 15 minutes it had. She called it a 1+ reaction but it got bigger after we left. I don't know if this means anything or if his reaction was mild because he's only had peanut once (other than in breast milk). She did let it slip out of her mouth that maybe he could be outgrowing it. Has anyone else had a neg RAST that still skin tested positive? We are still taking every precaution but hoping that his reactions would only be mild. I plan on having him re-skin tested before entering school. I'm praying that his blood wasn't mixed up in the lab!

On Apr 1, 1999

Ny son has only had the skin test, and based on his reaction there my allergist said the Rast testing would not do anymore. His wiel measured 20x20. the allergist considered this a MAJOR reaction. Has anyone else had this kind of reaction on the skin testing? As you may know, I am extremely apprehensive about this and his reaction.

On Apr 2, 1999

Hi Valerie -

It's scary to think about giving your child something you've worked so hard to avoid. I also thought about letting my child take a sniff at the allergist.......I'm still toying with that idea. I surely won't let him eat the stuff.... But "moderate food specific allergen"....what exactly does that mean? What would a sniff do........I've suspected two smell reactions......

The study by Hourihane does make some valid points. It does attempt to flag children who may not need to worry about a lifetime of peanut avoidance. However, being perhaps overly cautious, I tend to agree with the guy who bashed the study - you can check it out - RESOLUTION OF PEANUT ALLERGY - PATIENTS HAVE NOT BEEN PROVED TO GROW OUT OF PEANUT ALLERGY David, Tim BMJ 1998 Nov. 7; 317 (7168); 1317 PMID: 9804731, UI: 99023877.


20x20 is huge! When I was tested for ragweed by my allergist, my welt was 2 inches by 3 inches. He was surprised I never dropped just breathing air! He put 3 small shots of adrenaline into the welt itself. But would you believe, ragweed never really bothered me? All my seasonal allergies ever did to me (they have stopped since I've had children) was cause me to sneeze 30 times in rapid succession in the a.m. and that was that. Every now and then I'd take some Benadryl. So, I don't know exactly the relation to welt size and reactivity. Anyone know about this?

[This message has been edited by LauraP (edited April 02, 1999).]

On Apr 2, 1999

Laura- That's what makes me so skeptical about believing it would just be a minor reaction if our son was exposed to peanut. It seems like it is not an exact science, it appears to be all theory. For instance, our son was having bad hives and swelling when he would hug a dog but he skin tested negative until this last time (and the wiel was still considered small). I will always assume he could have a severe reaction to peanuts and treat it very seriously. It doesn't change our emergency plan at all.

------------------ Valerie

On Apr 2, 1999


My son also showed a very small reaction to dogs when skin tested, but last weekend he got around our dog and he had hives, and one eye was swollen almost completely shut. So I believe you are correct in speculating that even if the skin testing showed a very small reaction, the actual contact reaction may be much bigger.

On Apr 3, 1999

Hi Valerie, I thought I'd mention something I vaguely remember reading awhile ago since your sons's captest was neg and skin test sl. positive: Peanuts and Peanut butter commonly contain molds. I don't know how pure the pnt extact is that is used in the skin prick test, but it could be possible it is contaiminated with one of the pnt molds and one can be showing a positive reaction to the mold and not the pnt. I also read the same for dog allergies, people have tested false positive to the skin test because the dog allergen extract used in the test was contaiminated with another allergen (i think it was dustmites). I don't want to give you false hope, but maybe you could check into it or maybe someone on the board know something more about this.

On Apr 3, 1999

Hi Laura, I'm really confused about what you're saying about the cap rast test predicting clinical reactivity. What does that mean? Can it indicate how severe a reaction can be--ie, candidate for anaphyalaxis? The way I undestood it is all the types of tests can only predict sensitivity to the allergen and that there is not necessarily a correlation between sensitivity and degree of reaction.

If Dr. Sampson is right that the CAP rast can give you a fairly accurate indication of what would happen if your child ate a peanut, it would be really helpful to offer this test to all pnt allergic kids after they test postive by a skin test.

On Apr 3, 1999

[This message has been edited by brenda (edited April 03, 1999).]

On Apr 3, 1999


That is what Dr. Sampson says this test does. He told me that if my son scored a 15 or higher, don't even think about doing a challenge, because he could guarantee there would be a reaction. That's what makes the CAP test different from conventional blood testing. It is supposed to predict clinical reactivity..i.e., just what will happen if you eat it.

But, like I said above my son scored a 6, "moderate food specific allergen". I still don't know what that means, or exactly what would happen. I still treat peanuts like the plague. Yeah, it's not a 15, and that's a little comforting.....but what exactly happens to a 6? I'd recommed people have the test done. It'll give you another number to fester over....but say you score 15 or higher. Are you really going to do anything differently than you do now? But, I guess it's nice to know.

On Apr 3, 1999

Valerie, you have reminded me of an important point. Does your allergist have a "crash" cart in his/her office? If you are considering a challenge of any sort you might want to check this out.

On Apr 4, 1999

Coco, Thanks, I will DEFINITELY make sure they have a crash cart even if we're just doing an airborne challenge. If we ever did an oral challenge we would be in the ER (I'm not even sure I could let them do it then!). Being a nurse, I tend to fear the worst anyway. I would be very encouraged about the negative result on the RAST test but it sounds like there are a fair amount of false negatives. I would never even consider a challenge until he had 2 negative skin tests. Brenda, That's an interesting thought about the peanut molds. Maybe reactions to peanut molds tend to be milder. It's nice to fantasize that this could be the case.

------------------ Valerie

On Jun 10, 1999

This is not a medical response, just personal experience from an older pn allergic person: An allergist I consulted (in the 70's) refused to test me (I was an adult with a known allergy) because the test was too dangerous. When my children were born I assumed they were allergic (runs in my family). Eventually they got old enough to be curious and found the smell attractive. I promise you, allergic people find the smell violently awful. So if you are dealing with a child under the age of 8 or 9, assume the worst, prevent exposure and wait till later to determine if he/she is allergic. At that point, the conversation between the child and the doctor is more meaningful. Maybe today's tests are better than 20 years ago but for my money, why bother if you have any doubts. You cannot predict the severity of any possible reaction -- you have to assume it will be severe regardless of test results. Good luck!

On Jun 11, 1999

Um, I have to take exception to the statement that allergic people find the smell of peanuts awful. I personally find it quite attractive. I have had to train my self to take the faintest whiff as a warning, not an invitation to breath deep. And I am ana to the darn things, airborne AND ingested. [img][/img]