what is an allergy

Let’s start with the word allergy. When people hear the words food allergy, some people think that they have a pretty good idea about what that means.

The first thought is often of anaphylaxis, which is swelling of the tongue or throat that could be life threatening. This is typically the assumption when we are discussing, for example, a peanut allergy.

Of course there are other foods that can trigger an anaphylactic reaction, such as other nuts, shellfish, strawberries, milk, and eggs. And just about any other food has the potential to trigger an anaphylactic reaction. But thankfully, anaphylactic reactions to most foods are relatively rare, so you don’t often hear about them.

Based on this information, you might assume that food allergies are always severe or life-threatening. But then you might remember that sometimes a food allergy merely causes hives. Hives are irritating, itchy, and unsightly, but they aren’t life-threatening. Lots of different foods can cause hives, including peanuts. So a food allergy doesn’t have to be life-threatening, nor does an allergy to one particular food, such as peanuts, lead to the same symptoms in everyone.

Confused yet? If not, we’re just getting started.

Other people believe that food allergies are defined by the mechanism underlying the reaction. Different parts of the immune system can cause inflammation and thus symptoms. With most food allergies, it is assumed that an IgE antibody reaction is involved. IgE antibodies are produced by the immune system and can lead to histamine release, which causes inflammation.


An allergy is what results when your immune system is inappropriately activated. (img thx to nih.gov)

An allergy is what results when your immune system is inappropriately activated. Your immune system is designed to attack bacteria, viruses and parasites. It is not intended to attack the food you eat. But this is exactly what happens with some people. This is called a “food allergy” or “food intolerance.” 

When your immune system is activated, antibodies (also called immunoglobulins) are produced. Antibodies in turn trigger an inflammatory response. Inflammation causes pain and tissue damage, leading to further symptoms. Increased mucous production is another aspect of an immune response. 

When a food is broken down and absorbed, it is distributed through your bloodstream to all of your tissues. Therefore an allergic reaction can occur just about anywhere in your body. 

We don’t really understand why a food allergy can exhibit itself so differently in different people. However, every individual is unique and seems to have a unique weak point where symptoms of a food allergy show up first.

Image thanks to nih.gov