Allergy Testing For EE--including Patch Testing

Eosinophilic Esophagitis is a rare disease that causes an allergic reaction in the esophagus.  The allergic reaction is caused by white blood cells called eosinophils, whereas food allergic reactions are brought on by immunoglobulin E (IgE).  The eosinophils can cause a delayed allergic reaction, while an IgE response is more immediate.  Some children with EE can have both delayed reactions or IgE responses to an allergen.  Food is usually the main culprit for kids with EE, however, environmental allergies can play a role as well.

There are four different ways to test a child for food allergies.  The most common two are the skin prick tests and the blood tests (or RAST tests).  There is also patch testing and fresh food testing.  Below is a description of each:


Skin Prick Test

• used to test for food and environmental allergies
• performed by "pricking" the skin and placing a drop of the suspected allergen on the surface of the skin
• a positive reaction will appear in the form of a hive and redness at the site of the test in 15-20 minutes
• there can be false positives and, in the case of children with EE, false negatives

Blood Tests (or RAST tests)

• used to measure IgE antibodies to food and/or environmental allergens
• may be used when skin tests can not be used
• may be used when skin tests show no results
• may have false positives and, in the case of children with EE, false negatives
• does not predict the severity or type of reaction, but gives information on the likelihood of having a reaction if exposed to that particular allergen
• not as helpful in identifying foods that cause EE, but will identify foods that child has an immediate reaction to

Food Patch Testing

• used to detect possible delayed-type food allergies (common in children with EE)
• different from the the RAST blood test and prick test which are used to find immediate (IgE mediated) reactions such as hive or anaphylaxis
• a food patch test panel is placed in shallow aluminum canisters which is taped on the patient's back
• requires 2-3 trips to the allergist-to have the patches put on and again to have them re moved and have the results read 48 hours later, then again 72 hours later
• because many children with EE have a delayed allergic response to food, this test can provide more results
• may have false positives and false negatives

For more information on these three types of testing for EE visit the apfed website.  They also have a picture of patch testing.

Fresh Food Testing

• similar to prick testing
• used to test for food allergies
• small amount of fresh food, such as apple, is put on two pronged needle, then scraped under skin
• can be effective testing for oral allergy syndrome
• may have false positive or false negatives

When Andrew was first diagnosed at age 3, the doctor solely put him on steroids.  There was no mention of allergy testing.  He was on oral steroids for 6 weeks.  His symptoms continued, but it was not suggested that he be rescoped.  We stayed with that GI for 3 1/2 more years until Andrew's symptoms became much worse...constant stomach aches, chest pain, sore throat, regurgitation 20-40 times a day and finally vomiting after meals.  It was then that I knew we needed a new GI.  This new GI immediately recommended allergy testing.  Well, knowing what I do now, the true definition of EE, I often berate myself for the 3 1/2 years we lost in proper treatment for Andrew because he never had a complete food allergy panel.

This GI, understanding that EE is a delayed response allergic disease prescribed for Andrew to have prick testing, RAST testing, and patch testing.  The RAST testing showed nothing, the prick testing showed a positive result to soy only, but the patch testing yielded the most results with positive responses to chicken, wheat, milk, and treenuts.  After eliminating these foods from his diet for 3 months, he was rescoped, only to discover that his level of eosinophils had risen even higher than they were before we had begun.  So we decided to have him patch tested again, as well as fresh food tested.  This time he patch tested positive for strawberries, chicken, milk, treenuts/peanuts, fish/shellfish, eggs, wheat, rye, oats, barley and soy.  So we began a new elimination diet, taking all of these items out of his diet for 3 months.  Again, when rescoped his numbers went up.

As mentioned above in the description of the different types of allergy tests, each type of test can yield false negatives for children with EE.  Therefor, Andrew was still consuming foods that were attacking his esophagus.  Although we had taken out many of the culprits, we could have possibly introduced a new food to his system that he was allergic to (such as tapioca or millet) or because we were left with such few options, we could have been inundating his system with another food that his body was allergic to unknowingly (for example, perhaps corn).  Elimination diets are successful for many children with EE.  So don't let Andrew's story alarm you.  Andrew has proved to be a difficult case.  He is also one of the 5% of children who's biopsy did not clear after 8 weeks on an elemental diet of Neocate Splash. 

Although these tests can be time consuming and sometimes frightening for a child, they can give valuable information to the child's doctors.  Many children respond to an elimination diet of the foods that they test positive to.  However, it is important to remember that EE is a delayed response allergic condition and patch testing can be very beneficial in identifying trigger foods.  Many allergists do not perform food patch testing and you may have to do some research to find a clinic that does.  If your child tests negative to foods with   the prick or RAST testing and is still experiencing symptoms, it may be a good idea to find a clinic that performs patch testing.

Oh, and just a note, if you have a dog and your child gets patch testing done, be ready for your child to be your dog's best friend for the next 72 hours.  Our dog could not stop sniffing Andrew's back.  It was really quite comical!