Skin Prick Results

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I have a friend with a peanut-allergic son. She had him tested recently via the skin prick test and the results came back 5/7. She did not have a positive experience with his allergist and doesn't want to call back to get clarification on the results. Can anyone tell her what 5/7 for peanuts means for the skin prick test? Thanks.

Noreen

On Jul 23, 1999

Noreen, My son always gets the skin prick test, and I've never gotten a result like "5/7" before. I have been told that, on the skin prick test, it can go from a 1+ to 6+. My son always gets a 4+ for eggs and peanuts, and usually gets a 2+ for dogs, dust mites, etc. When the allergist sees the 4+, he always makes a funny, worried face and has indicated that a 4+ is fairly severe. I don't think he sees a 4+ that often. At first I thought that a 4+ was the worst, but I have gradually learned that it is not. Sorry I can't answer your question, but maybe the scale actually goes to 7 and she has a 5 out of a possible 7. Christine

On Jul 23, 1999

Hi Christine,

I guess I didn't probe my allergist well enough, because my son got a whopping 20+ for peanuts. while I knew the allergist was very concerned with the size of the wheal, I didn't know that a 6+ was the highest reaction. He also got a 2+ for beef and pork (shows no reaction to ingestion) and a 3+ for dogs and cats (shows reaction). Are you positive that a 6+ is as high as the score can get?

Thanks for your response, Debbie

On Jul 23, 1999

I'm wondering if the 5/7 is the size of the wheal. Perhaps it was 5 mm at first and then grew to 7 mm. According to an article on "Practice Parameters for Allergy Diagnostic Testing" published in the Annals of Allergy, Asthma, & Immunology, v 75 (6), December 1995, a prick/puncture test wheal response needs to be at least 3 mm to detect a specific IgE allergen. Quoting from the article:

"The larger the prick/puncture skin test reaction, the more likely it is to be of clinical significance. However, the presence of a positive prick/puncture skin test per se does not establish whether clinical sensitivity is present."

What makes skin puncture tests less reliable than RAST and CAP RAST tests on determining severity of reactions, quoting again from the article:

"Since it is impossible to quantify the exact amount of injected material by prick/puncture tests, allergic skin responses are dependent upon the skill of the individual tester, the reliablility of the device, the color of the skin, the status of skin reactivity on the day of the test, the potency and stability of test extracts (especially optimum concentrations), the depth of the puncture needle and the force, duration and angle of the application device. If these quality controls are not assiduously applied, interpretation of the tests could vary from one technician to another."

I read somewhere else (sorry, don't have the source before me) that a wheal needs to be at least 6 mm to guarantee sensitivity. My friend's son has had only one reaction to peanuts and it was rather mild. So I'm guessing that the 5/7 is a measurement of the wheal size, but I don't know where that puts him on the 1+, 2+, 3+, etc. scale. Does anyone know?

About 25 years ago, the size of my wheal for peanut was really large but my reactions were never that severe. I had the complete skin test panel done one year ago and, of course, no wheal for peanut. Now I'm allergic to things like redwood and cypress trees. Go figure.

Noreen

On Jul 24, 1999

Noreen/everyone - Spencer is having his first set of skin prick tests on Monday...can he have an allergic reaction from these? Do I need to bring extra benadryl and have the epi meds out and ready? I am unsure what to expect. We know he has a severe reaction from an unknown source (that was are trying to identify) and I am afraid if we find it he wouldn't be able to breath again. Thanks!

(P.S. He is category IV to Eggs and Peanuts that we found out about through RAST tests.)

------------------ Kelly M Another Mom in Michigan

On Jul 24, 1999

Debbie, No, I'm not sure if a 6+ is the highest reaction. I thought that is what my doctor told me in passing one time but I can't be sure. I just got the impression that Evan was close to the top of the reaction and he had a 4+.

Kelly, Evan has never had a real reaction to the skin test and I don't know if they would really do this if it was risky, but I guess anything is possible. What does happen is that about 5 minutes after the test, his back itches like crazy. It is a LONG 15 minutes. Then they come put some cortisone cream on the back and all is well. Christine

On Jul 24, 1999

I think maybe there are different skin prick measures. Or Ricky is truely super-super allergic. (His results seem to shock his doctor's and their staff) I got Ricky's results out to check. He had 9mm to egg white and peanut, 7mm to white potato, 6mm to chicken, 5mm to shellfish, 2mm to soy and beef. He has many +++ , ++++, for molds, grasses, tree pollen, cat hair,and dog hair.

His CAP RAST's, nine class VI's,three class V, seven class IV's, five class III's, two class II, and two class I. From there we did some additional food items which added three more class IV's(tree nuts) , seven more class III's (sesame seeds-highest doctor had never seen last year but Ricky's last test brought number down some still in same class), then we tested some fruits they are mostly class III.

To answer the question about skin prick tests it does expose the body to the allergin, possibly sensitiving it more! I will never have another skin prick test for Ricky as the second time he had this arm, sides of trunk and back huge welts. I have since read of kids who have had worse reaction.

On Jul 24, 1999

Kelly--I hope the dr isn't doing a skin test for peanuts? With a class 4 from RAST, he should not be tested because of a reaction. My son is class 4, and his allergist told me he would never skin test him for peanuts. I think you should have a talk with the dr before he does his tests.

On Jul 24, 1999

kelley, FYI: At the stamford FAN conference, Dr. Sampson said skin prick tests for peanut allergy is very safe. My daughter was skin prick tested and a had a weal that scored 4+, she did not experience any itching or pain from it. It is alway good to confirm with your doctor that he has in place all the necessary precautions in the event a rare severe reaction occurs (ie, epi and other necessary meds). Good luck.

On Jul 24, 1999

Hi Kelly:

I haven't run across any instance of an anaphylactic reaction to a skin test yet (doesn't mean it hasn't happened) but it can be uncomfortable if there is a significant response.

I'm assuming your son's allergist will not be testing for either egg or peanut since that allergy has already been confirmed by the RAST. Never hurts to double check, though.

From what I've read of the literature it seems the skin prick is what most allergists use in the case of your son, where they are trying to find an unknown allergy. Cost is a factor here, too, since the RAST and CAP RAST are more expensive in tracking down allergen X.

You have every right to be informed as to what emergency measures will be in place before the skin prick test is administered. Chances are your allergist will have the necessary Epi-Pens and Benadryl on hand for you.

One other thing, quoting again from the above article:

"Generally, fewer prick tests need to be performed in infants and very young children because these age groups are not likely to be sensitized to as many allergens as older children and adults. In younger patients, sensitization is more apt to reflect intense, prolonged exposure to allergens encountered earliest in life (i.e., foods, house dust mites, indoor molds, indoor insects and animal danders) rather than pollen."

In other words, there's a chance, even with the skin prick test, that not all allergens will be identified. Also, know that skin prick tests have the greatest incident of false positives than the other forms of allergy testing.

Noreen

[This message has been edited by Noreen (edited July 24, 1999).]

On Jul 24, 1999

Everyone - Thank you for your responses I feel a lot better about Monday. I have not spoken to this doctor yet since this is our first visit (we are switching allergists). I did call and confirm that they are doing skin pricks on the first visit, because of the anaphylatic (sp) reaction he had on 6/29/99 they don't want to wait.

I am in full agreement that peanuts and eggs are not necessary since we have had 2 RAST tests plus very strong reactions to both.

Noreen, the one thing the hospital was telling us was that most kids are not reacting to enviromental allergies until after age 2. I assume that is why they didn't test for them before.

Because we were able to rule out everything else Spencer came into contact before his reaction they feel pretty strongly that it is environmental. They told us that "when it happen before age 2 (like with him) it should be considered very serious and be prepared for a long road." This of course is not what we wanted to hear as we were pretty shaken up already.

It sounds a little like what you wrote. Did they mention anything about the severity vs. age of on set? I grew up thinking that if you get an allergy early it is good because you out grow it. Boy, have I had to reprogram my brain!

I will let you know what we find on Monday!

Thanks for your help!

------------------ Kelly M Another Mom in Michigan

On Jul 24, 1999

Hi Kelly:

A retrospective study on food allergies was completed back in 1987 at John Hopkins University School of Medicine.

(Ann Allergy 1987 Nov;59(5 Pt 2):179-82; Prospective studies in the natural history of food allergy.)

Out of the 177 infants and children surveyed, 60% to 73% of infants lost their food sensitivity in the first year and 26% to 53% of older children eventually remitted. Interesting enough, a large majority of children developed respiratory symptoms to inhalant allergens at the same time their food-related symptoms disappeared.

Perhaps this is where you might have heard that allergies had a better chance of being outgrown if developed earlier than later?

My guess is that more infants develop intolerances to milk or egg which are easier to outgrow. Outgrowing a peanut allergy, however, is far more difficult.

Noreen

[This message has been edited by Noreen (edited July 24, 1999).]

On Aug 5, 1999

I would not rely on a skin prick test. My son had one and it showed he was allergic with a 5. We had a blood test done and it showed he was not allergic. We did a food challenge in the doctors office and it also proved he was not allergic. As far as we know he was never exposed to peanuts it the past.

Elisa

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