Skin testing (and RAST testing) shows the body’s IgE immune response, which is an immediate reaction within the body. The most common symptoms of IgE allergies include rash, hives, swelling of mouth/face/throat, anaphylaxis, etc. Skin testing is supposed to be very accurate in testing for IgE mediated allergic responses. RAST isn’t quite as accurate, from what I’ve heard.
However, there is a lot of emerging evidence and new research showing that the body can also have IgG immune reactions to foods. This is still controversial, and not widely accepted by allergists. IgG immune reactions (some call these allergies, some call them intolerances) are delayed, and are therefore hard to determine. They can take hours to days to show up. This means your child could be having runny nose, irritability, sleep problems, etc. today, but that could be due to a food that they ate today, yesterday, or the day before. Very common IgG reactions to milk (usually to the proteins casein or whey) include runny nose, chronic ear infections, dark circles under the eyes (a.k.a. allergic shiners), eczema, changes in bowel movements (usually to either extreme: loose stools – about 75% of kids, or constipation – about 25% of kids), and sleep problems (difficulty falling asleep, or night waking). Kids can also be overall irritable, cranky, oppositional, etc.
For anyone suspecting milk problems and traditional skin prick testing (or RAST testing) doesn’t show anything, it is best to do a 6 week completely milk free trial, then do a milk challenge to see if symptoms show up. If you do this, you would have to be 100% milk free – no hidden dairy in breads, crackers, baked goods, margarine, sauces, soups, salad dressing, chocolate, etc. and obviously no milk, cheese, ice cream, etc. There are lots of great milk substitutes you could use during this period, but I would avoid all animal milk, including goat’s milk since it contains casein as well. After 6 weeks of going dairy free, you would then reintroduce some milk products and watch for a reaction. Remember, the reaction could take a few days to show up. This is traditionally the best indicator of intolerances.
However, there are labs that perform IgG allergy testing (sometimes called ELISA testing), but this would likely be an out of pocket expense, since this type of allergy is not yet widely recognized and accepted by the majority of the medical community. There are only a few labs in north america that do this type of testing, so you would likely have to have a local doctor order the test, have a local lab draw the blood (it’s only 1 vial) then have the serum shipped to the lab doing the testing. The one drawback to IgG testing, is that the IgG antibodies will only be present if the person is currently eating the food in their diet. So if someone is 100% milk free, for example, the IgG response to milk would likely be negligible or nonexistant. I would really only recommend IgG testing if the child has serious behavioural and sleep issues (for example kids with diagnosed or suspected autistic spectrum disorders, ADHD, severe sensory integration disorders, etc.). If this isn’t the case, then a food challenge is usually the easiest and best determinant of food intolerances likely due to the IgG immune response.
We had Ben’s IgG testing done through the Great Plains Laboratory in Lenexa, KS. He showed no reaction for milk, soy, wheat, egg, etc. via skin testing (IgE) but significant reaction those and other foods on IgG testing. Since removing these foods, and others that showed a moderate to high reaction on the IgG testing, we have seen a world of difference in him – especially in his behaviour and sensory integration issues! I can’t even begin to describe it! He is a much happier boy – not constantly irritable, no more daily tantrums, etc. Even my MIL mentioned what a difference she saw in him (and we all know what a huge thing it is to hear a positive comment like that from a MIL!
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Sorry for the long-winded response! I’ve literally spent the last 6 months studying this topic day and night while trying to get Ben back on the road to health, so I guess I’ve got a lot to say!
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