Milk allergy testing

Poornima asked, “Are there any tests that are conducted to confirm that a child has milk allergy? My child is 4 and is on soy based milk (she was on cow’s milk for almost a year). Even now she eats cheese, pizza etc. cannot eat yogurt. She did not break into hives or anything like that. May be a test could prove that she is allergic to milk protein.”

I know when people ask about tests they mean something fancy and mysterious: a blood test, or a skin-test done at the allergist’s office. But in reality, the “gold standard” best test there is for allergy is called a “double blind placebo controlled trial.” That is, you package up some of the potential allergen (in this case, milk) in such a way that the child and the parents don’t know it’s there. Then give some to the child. If the allergic-type reaction occurs when the child gets the genuine milk, but not when given a milk-substitute, than there is a milk allergy. No other tests are necessary.

Often, it’s not practical to so a trial like this. It’s difficult to set up a situation where the parents don’t know what the child is eating. Also, if the reaction is potentially severe or life-threatening, a trial may not be safe. That’s where allergy testing comes in. It’s a way to safely and practically see if a child is likely or unlikely to be allergic. But keep in mind that testing is an inexact substitute for a trial of the food. In other words, allergy testing will never tell you if a child is or isn’t allergic—it will only tell you if allergy is likely or unlikely. That’s a big difference.

There are two kinds of allergy testing widely available: blood tests and skin prick tests. The best blood tests are based on measuring IgE antibodies to specific allergens, and are often called “RAST” testing. Older tests involving IgG or IgG subtypes are inaccurate and used by notorious quack labs. These should be abandoned. Skin prick testing is done at an allergist’s office, and involves scratching or pricking the skin with a little bit of the allergen. Then, if a hive pops up, there’s more likely to be an allergy. Both blood tests are skin prick tests can have both false negatives and false positives, and should be interpreted with caution.

The most important allergy “test” is the history of what reactions have occurred in the past, and what happens with the food exposure. If possible, a great way to find out if a food triggers an allergy is to try to give the child the food to see what happens. This may not be safe, so talk with your child’s pediatrician before doing this sort of experiment yourself.

Explore posts in the same categories: Medical problems, Nutrition

Tags: allergy, child, food, testing, toddler

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