How common are food allergies in children?
The issue of food allergies is a complex one, probably because the food we eat is complex stuff. Many parents observe that particular foods don’t agree with their child. Pain, bloating, and diarrhea are all symptoms that can be evidence of this. Often such parents will say that their child is “allergic” to a particular food that they see causing those sorts of symptoms.
A broader term for this is food intolerance, the observation that particular foods upset the child’s digestive system. There are many examples of this kind of thing. One of the most common is a deficiency along the intestinal wall lining of lactase, the enzyme that digests the sugar lactose. This is not an allergy — it means that the person is intolerant of lactose, the sugar in many milk products. This lactase deficiency may be inherited or acquired later. (You can read more about this problem here.)
To a physician, the word “allergy” has a very specific meaning: it means that parts of the child’s immune system are reacting to components of the food. A common offender is peanuts (about 1% of all children), but there are many others. The symptoms of these true allergies can be much more severe, and typically cause problems outside the digestive system. Hives and difficulty breathing, either from wheezing or from swelling in the throat, are not uncommon. We occasionally see children in the PICU who have these more severe reactions to food. Parents of such children often need to have an injectable medication, epinephrine, handy at all times if this happens.
How common are food allergies and intolerance? A recent study in the journal Pediatrics gives us some answers. The authors found that in 2007, 4% of children under 18 had some form of problem with food. This was an increase of 18% over the previous decade, although it was unclear if this was a real increase or simply reflected increased awareness among parents and physicians. This particular survey, although broad, did not distinguish between allergy and intolerance. However, the authors noted that it correlated with other, smaller studies in which true allergy was documented with specific tests. So it seems like a real phenomenon