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  • For some people, a simple peanut or a bite of a shrimp can cause the body's immune system to wildly overreact.

  • In some cases, the results can be deadly.

  • But what exactly is happening in the body for it to confuse nuts or shellfish with a true threat?

  • By definition, a reaction to a food is only considered an actual allergy if the immune system is involved.

  • And if the response is caused by immune cells called IgE antibodies, which we'll get more into later.

  • But it's important to distinguish an allergy from a sensitivity or an intolerance, which

  • involve uncomfortable symptoms as a reaction to food, but don't cause an immune response.

  • So if you're lactose intolerant,

  • you're not allergic to milk.

  • Hi. My name is Tina Sindher.

  • I'm a Clinical Assistant Professor in allergy and immunology at Stanford University.

  • And I see patients in my clinic with, eczema, with asthma, food allergies, with environmental allergies.

  • And my main focus lies in food allergy research.

  • In order to understand food allergies, we need to know how the body evaluates food in the first place.

  • In a typical immune system, your body is constantly evaluating different antigens to deem them

  • either benign or dangerous, in this case, the proteins on the food particles.

  • When they eat a peanut for the first time, their body kind of tells your immune system,

  • like, look at this, this is a peanut, do not fight this in the future.

  • So that every time they eat a peanut, their immune system does not react to it at all.

  • The immune system is basically building up a tolerance for the next time peanuts are around.

  • But in the allergy afflicted, by the time they eat something like a peanut, their body

  • is already primed for an immune response.

  • Our immune system is kind of like a seesaw, it needs balance.

  • So, on one side of the seesaw is your T regulatory cells.

  • And they are kind of your brakes.

  • They're the cells that tell your immune system, calm down, slow down, do not fight this.

  • And then the Th2 is your allergic cells.

  • And they are ready to go, and revved up.

  • And they will bring in all other inflammatory cells to fight what they perceive as danger.

  • In most people, the T regulatory cells hold more weight in determining what's problematic and what's harmless.

  • But in people with a more Th2-skewed system, their cells sound the alarm much more easily

  • and have a high sensitivity to the harmless proteins on foods, most commonly milk, eggs,

  • wheat, soy, peanuts, tree nuts, fish, or shellfish.

  • But having a skewed immune system isn't enough, there has to be a trigger point to

  • developing a specific allergy, and that's still not completely known.

  • One of the proposed thoughts on how allergy begins has to do with the allergen entering the body the wrong way, through the skin.

  • Minuscule food particles floating in the air can enter the body through the skin if there

  • is dysfunction in the skin barrier due to something like eczema.

  • We're talking about nanoparticles of peanuts.

  • So it can be in your bedding, it can be in the air.

  • You might be getting exposed to it without any knowledge of it.

  • It's that it's entering our, it's interacting with our immune system in a way that it's not meant to.

  • We're not supposed to get food allergens to come in through our skin. Or environmental.

  • So really the initial process is the barrier breakdown that we're seeing.

  • So, in some people, when immune cells in the skin encounter these antigens, they recognize

  • that they are foreign and in the wrong place.

  • This ultimately signals the immune system to produce antibodies called immunoglobin

  • E or IgEs to fight against the food proteins.

  • Now, when this same food is finally ingested the right way through the mouth, the body's

  • IgE's will recognize it as a threat and respond in full force, leading to an allergic reaction.

  • And the way this looks is basically, when your mast cells and basophils open up, they

  • contain histamine and tryptase, and a bunch of other inflammatory mediators.

  • And those are what drives the reaction.

  • This inflammatory response mirrors the body's reaction to a parasitic infection.

  • But, skin exposure is not dangerous for those with food allergy already.

  • Our body shouldn't be responding like that, right, to food, and that's what we're hoping

  • to figure out, and that's what we're hoping to prevent.

  • We know that our immune system has developed this kind of response, but we don't know the why.

  • There is a genetic component to who has allergies and who doesn't.

  • Children whose parents have allergies are more likely to have allergies themselves.

  • But there are other environmental factors at play that mess with the balance of the

  • seesaw of an individual's immune system.

  • So it's not one thing, it's multifactorial.

  • And it's our diet, it's our lifestyle, it's modern conveniences that may push us kind

  • of over the edge for some, not all, but some.

  • The thing is, we might just be too clean.

  • This is what's known as the hygiene hypothesis which says that a lack of exposure to germs

  • early in life can trigger the immune system to mistake a food protein as an invading germ.

  • So for fewer allergies, maybe...

  • Get a dog, roll around in dirt, don't wash your clothes, and play in the sun.

For some people, a simple peanut or a bite of a shrimp can cause the body's immune system to wildly overreact.


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食物アレルギーの原因は? (What Causes Food Allergies?)

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    Jerry Liu に公開 2021 年 01 月 14 日