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
Allergies are caused by our immune system responding to non-dangerous substances as if they were actually very dangerous. This means that sometimes you can develop an allergy after repeated exposure to something (though in some cases you can actually build up a tolerance after repeated exposure), but it also means that it can happen spontaneously or be caused by genetic factors.
To simplify things somewhat, your immune system makes a type of immune cell called a B Cell. B Cells only have one job: they make antibodies. An antibody is a protein shaped a bit like a fork, where the tip of the fork will recognize and bind to one specific type of thing, be it the outside of a virus or a bacteria, or something that is normally benign like peanut oil. Your body is constantly producing new B Cells, each of which makes just one type of completely unique antibody that recognizes something totally random. B Cells that recognize things your body naturally produces are killed off (and if they aren’t you can develop an autoimmune disease), but the rest are simply released into your body to maybe someday meet their specific target and start the larger process of an immune response.
For an ordinary person, when their immune system detects something like peanuts, it will quickly recognize that there isn’t a danger. But sometimes your immune system can get confused, and think that something terrible is happening. When this happens your body tries to fight off the ‘invader’ by rushing a lot of blood to the area (which brings things like white blood cells and other types of immune cells), which causes swelling. If this happens in your throat, it can cause breathing problems, but if it happens somewhere else like your skin it can cause a large itchy rash or other similar symptoms.
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)?
I’ll preface by saying that I am not a doctor or allergist. Just someone interested!
From my understanding, babies can get allergies early on because of things like genes passed down from their parents which can make them more likely to have allergies. They can also be exposed in different ways and react to certain foods or things in the environment – for example, cow’s milk or eggs if given too early, exposed to allergens through breast milk if parent eats foods that can cause allergies, things in the environment like dust, pet hair, pollen.
When someone has an allergy, it’s like their body’s alarm system gets mixed up. Normally, the immune system protects the body from harmful things like germs, but with allergies, it sees harmless stuff (like peanuts or pollen) as dangerous. So, when a baby with an allergy eats a food they’re allergic to or gets exposed to something they’re allergic to, their body tries to fight it off. This fight can cause symptoms like itching, swelling, or trouble breathing.
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