Back from the allergist--some answers, hoping for more

Posted on: Tue, 10/02/2001 - 6:25am
BENSMOM's picture
Joined: 05/20/2000 - 09:00

We took Ben to a very well-known allergist in Baltimore today. His name is Dr. Wood and he has worked with Dr. Sampson in the past. This is the third allergist Ben has been to, because I am trying to find out why he tested 4+ for peanuts on a skin prick test but has never reacted. He's never eaten a peanut or pb, but he's eaten products with peanut flour and picked peanuts off food and eaten them before he was tested. So here are some things I found out.

-only about 30% of the people who test positive for food allergy with a skin prick test are truly allergic. Only 30%!! So what's the value of a skin prick test? It is very accurate if it's negative. If it's positive, it really doesn't tell you much. There is really no correlation to severity of reaction if it is very positive vs. slightly positive, and there are lots of false positives. I think he said there are more false positives in generally allergic people. The skin and blood can have IgEs for all kinds of things that the person might not really react to (so same false positive problem with blood tests, but not sure if the rate is as high). Also, the way the allergen in the serum is mixed can affect the outcome of a skin prick test.

-20% of grass allergic people will test positive to peanuts through a skin prick test. I think he said this is true for a blood test too. Ben is allergic to grass.

-there are different proteins in peanuts that people can be allergic to. They have not found any correlation between which or how many proteins someone is allergic to and the severity of the reaction. However they do seem to be finding that a person is more likely to outgrow the allergy if they are allergic to one of the proteins vs. the others. Don't know any more details.

-We've all heard they are working on an anti-IgE therapy to cure or mitigate reactions. But what are IgEs supposed to be good for in our bodies? They are there to fight off parasites. In developed countries they are not really needed. If someone on anti-IgE therapy went to an undeveloped country, they would be at higher risk of contracting a parasite.

-I told him that my 3 yr old daughter used to eat nuts and pb, but we took her off them when we found out Ben was allergic, when she was 2. I asked if we should keep her off until she's 5 and he said that if she ate them with no problem before then she's unlikely to develop the allergy. She doesn't appear to be an allergic child.

-I asked if we should keep Ben away from shellfish, and he said that since he is an allergic child (seasonal allergies, cat, used to have eczema, slight asthma when sick) that he is at a very very slightly higher risk to develop a shellfish allergy, but it's not something I really need to keep him off.

-Would a false positive skin prick test mean that the person is more likely to develop that allergy? No, as I said above, allergic people tend to develop IgEs to things they won't react to.

-Ben has also had problems with bananas, cantaloupe, watermelon, and other melons. These are all related to ragweed--they cross-react because the protein structure is similar. By controlling the ragweed allergy, he should be able to better tolerate the fruits. It would be extremely unlikely that his reaction to any of these fruits would go beyond an itchy mouth or swollen lip since it is due to cross-reactivity. He doesn't want to eat any of that stuff, but I don't have to worry about picking grapes out of a bowl of fruit salad and giving it to him.

-He got a CAP RAST and the results will take 2 weeks. For peanut, if it is 0-5, it is 60% likely that he is not allergic and he will have an oral challenge. If it is 5-10, it is 10% likely that he is not allergic. The doctor may still recommend a challenge since he has no history of reaction. There is still a good chance it could be higher due to a false positive because of grass allergy or general allergy, or that he is actually allergic and never had enough to react. So, I'm hoping for a low number to finally have an answer, but I'm not that optimistic.

Whew! I think that's all folks! I hope this helps someone, especially those of you who have kids who tested positive but never reacted.

Posted on: Tue, 10/02/2001 - 6:39am
anonymous's picture
Joined: 05/28/2009 - 16:42

Wow - Thanks for sharing!!
It sounds like you have some positive things to think on for awhile! Yeah for your family!! [img][/img]
My son is also allergic to grass, cat, dog, dust mites, mold, and penicillin (along w/P/TN). He has had reactions to ingestion. He has also had the skin prick and the blood test. We know our fate, I'm afraid, but I still have prayer!!! [img][/img]
Well wishes to you and your son!!
Take care,

Posted on: Tue, 10/02/2001 - 8:51am
julieb's picture
Joined: 07/21/2001 - 09:00

bensmom, thank you for all the detailed information! My son (almost 2) had a skin prick test for pb and tested over 4. According to the allergist, my son would be in the ER if he ate pb.
Months later, my son had to have an IgE RAST test (this is before I knew about CAPS) since he skin tested positive then negative to some food allergens and negative then positive to other food allergens. But, that allergist NEVER suggested a baseline blood test for my son's peanut allergy when we did the blood draw! And I was just learning still about the allergy that I didn't know better.
I am switching to a new allergist who already wants to get that baseline. My son is going to have endure another blood letting at the hospital. But, your post gives me some hope that maybe, just maybe, that original skin test for pb is wrong. Fingers crossed. And thank you again for the education. Warmly, Julie B.

Posted on: Tue, 10/02/2001 - 9:22am
DRobbins's picture
Joined: 07/19/2001 - 09:00

Quote:Originally posted by BENSMOM:
[b]I told him that my 3 yr old daughter used to eat nuts and pb, but we took her off them when we found out Ben was allergic, when she was 2. I asked if we should keep her off until she's 5 and he said that if she ate them with no problem before then she's unlikely to develop the allergy. She doesn't appear to be an allergic child.[/b]
I have to disagree with this. When my oldest child (now allergic to peanuts) was an infant, I read that I should keep him away from peanuts until age 3 since that would make him less likely to develop a peanut allergy. Even though we had no family history of food allergies, he never had any peanuts or peanut butter other than a single bite of a Reese's pb cup at age two-and-a-half, which he didn't care for, but didn't react to.
He never liked trying new foods as a preschooler, but began eating peanut butter every so often. By the time he was 4 or so, he started eating it more often, and by 5 was eating a beanut butter and jelly sandwich for lunch most days. Soon after he turned 6, he developed his peanut allergy.
So I have to say that your doctor's belief that a child who had previously done fine with peanuts is unlikely to develop a peanut allergy is incorrect. It might technically be statistically correct, since most kids don't develop peanut butter allergies anyway, but a previous history of not being allergic to peanuts does not imply that the allergy won't develop, especially given a history of peanut allergies in the family.
For what it's worth, my non-allergic younger child (4 years old) is not allowed to eat peanuts or treenuts, and I will continue to withhold them for quite a while, probably until age 8 at least (a couple years past the point at which my older child developed his peanut allergy).
Good luck. I hope that your child's allergies turn out to be just false positives.

Posted on: Tue, 10/02/2001 - 10:07am
BENSMOM's picture
Joined: 05/20/2000 - 09:00

Debbie, does your oldest child have other allergies, or asthma or eczema? Just grasping at straws here. Anyone can develop an allergy at any time, and I told the doctor that a 30 yr old friend had just developed an allergy to shrimp. He said that it is common for shellfish allergy to have an adult onset. I developed allergy to cats as an adult. But he said it would be unlikely for my daughter to develop a nut allergy at this point.
Obviously your son's experience shows it is quite possible. I think that even if Ben is not allergic to peanuts after all, it will not be a staple in our house. He doesn't like it. I would LOVE to be able to whip up a pb&j when there's nothing else easy to eat, but I don't think it will ever be something common. I think we will wait for Eliza to be a bit older, just to be safer. Of course it's always possible to develop the allergy at any time, but to take reasonable precautions, maybe we will wait until she's 5 after all. If Ben turns out not to be PA, I think we'll still stay away from peanuts, but not worry about cross-contamination. It's something we'll have to think about. Thanks for sharing your experience.

Posted on: Tue, 10/02/2001 - 10:55am
GPMac's picture
Joined: 10/02/2001 - 09:00

HI I am VERY new here. What is a CAP RAST & a IgE RAST?
My little girl just had a skin prick test. Many things were put on her back but they only pricked the peanut & she just reacted to the thay one.
Is this test rated on a # system? I notice some people have #'s. I didn't see any #'s on her paper work that they gave to me.
So I take it there are better tests out there?Oh and one more thing....My allergist told me just to keep her away from nuts and there was no need for an epipen as of yet.
I think I need to see another Dr. hay?

Posted on: Wed, 10/03/2001 - 12:54am
BENSMOM's picture
Joined: 05/20/2000 - 09:00

GPMac, I read your post on the introduction board and see that your daughter has had a reaction to peanuts. Yes, I agree with everyone that you need a new doctor.
There are different RAST tests, but the CAP RAST is the newest I think. It measures the IgEs to the allergen in the blood. When you're allergic to something, your body produces IgEs to that particular allergen. (Someone please correct me if I'm wrong.) The CAP RAST does have some murky correspondence between the number and the likelihood of a reaction (but not the severity). You might want to get this test done as a baseline, and then get one every year or so to see if the number comes down, indicating your daughter might be outgrowing the allergy.
Skin prick tests also have numbers, 0-4 I think. 4+ is very severe, but as I said in my original post, it doesn't seem like the number means much. A negative skin prick test is pretty reliable, but a positive one doesn't tell you much. You know your daughter is allergic from her reaction, and the skin prick test confirmed it. It isn't going to tell you more than that, and it could still be positive if she outgrows it. Hope this clears it up a bit.

Posted on: Wed, 10/03/2001 - 2:15am
DRobbins's picture
Joined: 07/19/2001 - 09:00

Quote:Originally posted by BENSMOM:
[b]Debbie, does your oldest child have other allergies, or asthma or eczema <...> But he said it would be unlikely for my daughter to develop a nut allergy at this point.
Obviously your son's experience shows it is quite possible [/b]
My older son, the one who developed a peanut allergy at age 6, had a brief period of a bit of dry skin as an infant, which the doctor said was eczema. (It was so mild, though, that it didn't really matter what it actually was, since the treatment was to put moisturizing lotion on it in any event [img][/img] It went away quickly. ) He does not have asthma, although at this point, it wouldn't surprise me if he developed it at some point in his life [img][/img]
At age 5, he developed hay fever. At age 6 came his first food allergy, peanuts, despite eating peanut butter with no problems for a couple of years.
Because of his peanut allergy, we substituted soynut butter and jelly for his peanut butter and jelly sandwiches. After 6 months of this, he became allergic to soy and strawberries (the flavor of jelly we were using). I'm convinced that the soynut butter triggered the soy allergy, because he was eating more soy on a daily basis in that one soynut butter & jelly sandwich than he'd been eating in a couple of months, pre-peanut allergy. I think we just overwhelmed his system with a food known for being highly allergenic. In case you can't tell, I'm still kicking myself over this one. [img][/img]
For what it's worth, I think your approach of restricting your daughter's peanut intake in obvious forms, but not being hyper-vigilent about cross-contamination makes a lot of sense.
And again, I'm keeping my fingers crossed that your older son's peanut allergy turns out to be a false alarm. Is there a smilie for crossed fingers? [img][/img]
Best wishes,

Posted on: Wed, 10/03/2001 - 6:04am
GPMac's picture
Joined: 10/02/2001 - 09:00

Bensmom please tell me how do they do this CAP RAST thing? Will I have to expose my child again? You say this test is pretty new? Let me get this right...this will give me a base line to see if my child eventually out grows it or it could tell me she is not allergic? I wonder if it is here in Canada yet?
Do you have any links on it?
You have given me some hope when my MIL exposed my child to PB she also exposed her to a few other new things.
Thank you

Posted on: Wed, 10/03/2001 - 7:57am
Liamsmom's picture
Joined: 02/21/2001 - 09:00

Great note-taking, Bensmom! I lapped up every word of your post, and am about to forward the thread to my husband. We never have time for all our questions during Liam's rare appointments with his allergist. So it's fascinating to read about the experience of other families -- even more so when they're seeing doctors who are particularly knowledgeable about food allergies. You addressed several issues I've been wondering about. Thank you for sharing this information!

Posted on: Wed, 10/03/2001 - 8:00am
BENSMOM's picture
Joined: 05/20/2000 - 09:00

GPMac, the CAP RAST is a blood test, and yes it is available in Canada. So, no, your child won't be exposed to the allergen again. I hate to get your hopes up--it was probably the pb your daughter reacted to.
Debbie, actually it is worth something to me that you agree with the approach I plan to take with my daughter--thanks. She really won't have anything cross-contaminated while she's with her brother, but if she's in preschool, I won't worry about cross-contamination. I will also take a lesson from you and try not to expose Ben to any highly allergic foods in large amounts. Several people I know give their kids soy milk instead of cow's milk. I've always been afraid to do that. I use rice milk. (Ben used to have a dairy problem so I took him off cow's milk.)


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