Hi all! I work in a daycare/preschool center and a few of our kiddos, even our infants and toddlers have an allergy (eggs, dairy, etc.)
What I’m curious about is how they can be so young and already be allergic to something? You could say it’s because of their environment.. but at that age they are either at home or at daycare. How exactly do they get exposed? And how does our body know certain foods or substances are dangerous?
Please and thank you!
In: Biology
Let’s preface this by saying there are unknowns at every corner, and any conclusive-looking answer is going to be loaded with caveats.
>What I’m curious about is how they can be so young and already be allergic to something?
People develop allergies at all ages. It’s stranger in the sense of immunological memory to become allergic to something at a later ages after having tolerated it for a long time.
>You could say it’s because of their environment.. but at that age they are either at home or at daycare. How exactly do they get exposed?
Many *but not all* allergies are driven by mast cells, equipped with a particular flavor of antibodies produced by B cells. Antibodies are proteins whose one end can bind to something, and that something is dependent on the exact shape of the antibody, which is randomly modified by every B cell. This means there is an incredible variety not just in the different targets (“antigens”) antibodies can bind — influenza hemaglutinin, SARS2 spike, birch pollen… — but also the exact spot (“epitope”) on an antigen.
And that exact epitope is all that matters; if something similar enough appears in an antigen different from the one that provoked the antibody response originally, that doesn’t matter. If it’s chemically similar enough in that one spot, the antibody will stick. That’s why some but not all people are allergic both to certain pollen and certain grasses; there are similar epitopes to be found in these antigens, but whether your pollen response ends up targeting the bit in the pollen that also appears in grass is a matter of chance.
All of which is a long way to say that we can become allergic to things in an indirect manner.
>And how does our body know certain foods or substances are dangerous?
Contextual clues. Is the antigen accompanied by generic signs of trouble, like bits of bacterial flagella or virus-derived single stranded DNA? Where are we encountering it — in the gut (probably food, we can be less alert) or under the skin (not a place we should be seeing stuff for the first time unless it got in uninvited)?
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