Indefinate Diagnosis - Conflicting Rast and Skin Tests

Posted on: Sun, 09/14/2003 - 7:27am
SweetAmanda's picture
Joined: 03/31/2002 - 09:00

My 8 yr old daughter is very allergic to peanuts and nuts. When she was diagnosed at 4 yrs, I had my then 10 month old son skin tested. It was negative. I was told that because of his age it may not be absolutely definitive. Since then, we have protected him from exposure to peanut and nuts. ( Which was easier for us because of my daughter's serious allergies.) Before he started Jr. Kindergarten two weeks ago, we decided to have his skin test repeated - if it was again negative, the doctor was going to do a food challenge so we could be sure he is indeed negatice to peanuts and nuts. To my horror and utter disbelief, he was positive to Almonds, Hazelnuts and Peanut. We then did a Cap Rast - which was completely negative (totally non reactive). Our doctor was very surprised. He said almost always when someone is allergic the skin and RAST tests match. Ten days later we repeated the skin test and again it was positive. The doctor says his guess is that my son is not allergic. We now need to perform a food challenge in a hospital setting. The hospital is scheduling out one year from now. So, my son has completely negative blood work and no reactive history whatsoever, yet we must act as if he is allergic, even though he probably isn't, for at least a year. Even though he would never eat peanuts or nuts because of my daughter, as you all know, training the school, his friends and their parents, etc. is tough and stressful. It is tough not having a difinative diagnosis. I feel like I am on an emotional roller coaster, and will be for at least a year. Any advice? I am desperate. Thank you.

Posted on: Sun, 09/14/2003 - 8:08am
Sandra Y's picture
Joined: 08/22/2000 - 09:00

I will merely second what your doctor said, which is that you need to treat him as if he is allergic because of the positive skin test.
But I think you can be very hopeful. With a negative RAST, I'd bet he's negative. Skin tests have a very high rate of false positives. If he has another negative blood test in a year, I'd feel quite safe letting him face a properly supervised challenge.
I wouldn't tell the school or anyone else that the diagnosis is indefinite. For now, all anyone needs to know is that he has tested positive for peanut allergy.
Good luck! I bet you'll be getting some very good news in about a year. I hope so!

Posted on: Sun, 09/14/2003 - 9:32am
Janet Laflamme's picture
Joined: 02/08/1999 - 09:00

We were in the same situation in regards to waiting a long time for our egg challenge. They asked if we wanted to be put on a list for any cancellations. We were lucky enough to get a spot a few months before our scheduled appointment. It can't hurt to let them know if you'd be willing fill a cancellation. Best wishes with the test.
[This message has been edited by Janet Laflamme (edited September 14, 2003).]

Posted on: Sun, 09/14/2003 - 10:56am
LDR's picture
Joined: 09/28/2001 - 09:00

Tough situation, but I bet you can be extremely optimistic about his chance of outgrowing the allergy. Truthfully, I'm not sure what the skin test tells us--my daughter reacted to water on the skin test! Some people just have very sensitive skin, or the stick used irritates the skin. How about repeating the labs? It would be nice to get a confirmation of those results.
My daughter was 18 months when she first reacted to peanut (on consumption). Our pediatrician told me to have my 3 year old tested, too. New to PA and not knowing anything, I took her to an allergist.
He thought it was meaningless to test for allergies without cause--for the very reason that there are a lot of high false positives for skin testing. He said it wasn't meaningful with no known reaction, and talked me out of the testing. I've been to another allergist since then, someone I have a great deal of confidence in, and she agreed.
I've never had my other daughter tested, and she's 5 1/2 with no known allergies.
As far as preparing teachers and play dates--
I know it's exhausting, but the good news know the drill. You know exactly what you need to do and say. I bet you can do it in your sleep! Hopefully next year you won't have to address this issue for your son.
Good luck!

Posted on: Sun, 09/14/2003 - 1:42pm
SweetAmanda's picture
Joined: 03/31/2002 - 09:00

Thank you for the replies. I guess there is no easy answer to my problem. My son is very fair, with very sensitive skin - the very type that tend to get false positives on skin tests. I will ask to have the blood work repeated. LDR...Did your now 5 1/2 year old daughter ever eat peanut before your younger daughter was diagnosed? If she had been exposed to peanut and had no reactive history, then I can see why you were advised not to test. Even if you had skin tested your daughter and it came out positive, if she is eating peanuts without a reaction she is not allergic. I have read that it is not uncommon for people who eat peanut butter every day to have extremely positive skin tests.

Posted on: Mon, 09/15/2003 - 6:30am
LDR's picture
Joined: 09/28/2001 - 09:00

You're right--my five year old did eat peanuts before without reaction, so the situation is different.

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