Skin vs. Blood Testing for Allergies

Many people have asked questions about the process of W's allergy testing and the difference between the skin and blood test, so I thought I would share a bit about it.  

Skin Tests

An allergy skin test involves pricking the skin with a trace amount of an allergen and then watching how the skin reacts. The nurse or technician administering the test marks the skin on his back so that they can track which reaction is the result of which prick.  With each of W's skin tests, a positive control (typically a histamine solution) and a negative control (saline usually) have both been administered along with the other pricks.  If I remember correctly, the far right two pricks were the negative (middle) and positive (bottom) in the below picture.  After all of the pricks are made, we wait and watch as hives form (or hopefully don't) on those spots.

I challenge all of you to try to hold a squirmy 3/5/9/ or 11 month old in your lap who has just gotten between 4 and 12 shots in their back, all the while not touching said shots and not letting them touch/itch/rub them either. Oh, and go ahead and do this for 20 minutes. Fun!

W's skin test at age 9 months

After the allotted time has elapsed (shout for joy) the nurse will come in and measure each of the spots using a series of numbers and words that can only be described as a foreign language: wheal, flare, pseudopod and satellites.

Apparently these numbers and words all mean something and correlate into a final ranking.  If your ranking is above a certain number (based on age) then you are considered to have a certain percentage chance of having an allergic reaction (see an example of W's results below.)  These numbers are measures of IgE antibodies released by a persons body in response to that allergen.

W's has had 4 skin tests during the first year of his life, the first at 3 and 1/2 months old.

Blood Testing
Between two different allergist and a few pediatricians, there have been conflicting recommendations on the best course of action to test for allergies. Some say blood tests are inaccurate before a certain age and some said the same for skin tests.  Because W's first reactions occurred before 6 months of age, the consensus was that skin testing was more accurate than blood testing.   Since then, W has had two blood tests  One at 7 months and one at 11 months old. For the most part, blood testing seemed to be ordered to either confirm a skin test allergy or to have a base IgE to compare against. 

Blood testing is just as it sounds, whereas a lab draws vials of blood and sends them off for testing. Unlike the immediate gratification, or lack there of, with skin testing, results take a few days to come back.

Results Example

Because eggs were the first know food allergy for us, it is the one for which W has been tested the most number of times. His first test (skin) at 3 and 1/2 months revealed an IgE level of 5. Children under the age of 2 years are considered to have a 100% change of reaction to eggs at a level 2. The rest of his testing for eggs are as follows:

7 months (blood): IgE level of 14

9 months (skin): IgE level of 30

Eggs will likely be tested again in the coming months to see if his levels continue to rise.

My Little Trooper

I have to say that my sweet boy is such a trooper. Counting only pricks and shots for allergy testing, W has been poked and prodded more than 30 times. While he does cry (I'd be more freaked out if he didn't) he recovers and is back to his sweet and happy self in no time.

Disclaimer: I dropped out of the pre-med program in my sophomore year of college, so please forgive my lack of medical knowledge and any scientific inaccuracies. I am writing according to my understanding and what memory remains after having three children.

The List Gets Longer - Part 1

So we had the diagnosis of an egg allergy long before the time that W's started on solid food.  Fast forward to 6 months of age and we gave him his first food, bananas.

At first there was no reaction. He loved bananas, but slowly we saw his cradle cap (which we thought we had under control) come back.  I had my suspicions and so when I started feeding him apples next, we stopped the bananas.

The third food we tried was avocado.  He didn't seem to like it too much, but I kept trying, spooning it into his mouth. He threw it up.  And by that I don't mean he spit up or gagged because he didn't like it.  It was full on Linda Blair in baby form.  We abandoned the avocado and went back to bananas only to see the same results with the bananas but on a larger scale and with hives to boot!

Back to apples.

For around 2 months we would try one food a week with several attempts resulting in throwing up or hives.  Each time...back to apples.

Our NO list now included eggs, bananas, avocado, kiwi, potatoes, carrots, sweet potatoes and lamb.  We found a wonderful allergist who took my call every Friday morning to discuss what food to try next and we found success and a YES list that eventually got longer than just apples.

The Gnome King

As a child of the 80's, the cult classic, "Return to Oz", inspired both fascination and fear. The scene where the villainous Gnome King is defeated by swallowing a chicken egg (which are deadly poisonous to gnomes) now resonates on a whole new level for me.

These days I find myself living in fear of eggs. Panic stricken by even having them in my refrigerator (double wrapped in plastic bags and hidden in the back in case one of the children decides that raw eggs would be such a great snack!)  Just the mention of French Toast at daycare sent me into frenzy. Why?

When W was 3 months old I was making a quiche for dinner.  Just as I was finishing up my prep, W started to get fussy and by the time I had the quiche in the oven, he was screaming.  In a hurry to get him, I washed my hands quickly (not carefully) and picked him up. Within minutes hives started to appear all over his face, arms, and torso.  Just a bit later, one eye began to swell.

After a dose of Benadryl we rushed him to the pediatrician who told us that it looked very much like an allergic reaction.  A visit with the allergist a few days later confirmed that W was allergic to eggs and that his reaction was brought on through contact with the egg.

The level of allergies is measured by IgE, Immunoglobulin E, which is a type of antibody that goes into action when a allergen is present.  In order for W to be labeled as allergic to eggs his level needed to be 2 or higher when egg is present (this is for children under the age of 5). His first testing at 3 months resulted in a 2.  At 7 months, his level was a 14 and at his last test at 9 months, it was 30.

How sensitive is he?
He has reacted by touch twice, and has broken out into rashes twice when eggs were being cooked around him. He cannot have the white or the yolk (the white is usually the more allergy provoking part anyways).  From what we can tell, he doesn't react to baked goods when he touches them, but he can obviously not eat them.

Will he grow out of his allergy?
80% of children grow out of an egg allergy.  This being said, his testing shows increases of IgE not decreases.  Out of all of his allergies, the egg is the worst for now, and Eggs Benedict will likely be off the menu for life, but I have every hope that he will one day be able to eat piece of cake or a brownie.

So that was how our allergy story began and why I can never look at Fairuza Balk the same again.