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What Causes Food Allergies? – Transcript
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- An actual food allergy involves the immune system and IgE antibodies, distinguishing it from a sensitivity or intolerance.
- In people with a Th2-skewed immune system, cells have a high sensitivity to harmless food proteins and sound the alarm easily.
- One proposed theory suggests that food allergies can begin when minuscule food particles enter the body through the skin due to barrier dysfunction.
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For some people, a simple peanut or a biteof 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 bodyfor it to confuse nuts or shellfish with a true threat?
By definition, a reaction to a food is onlyconsidered an actual allergy if the immune system is involved. And if the response is caused by immune cellscalled IgE antibodies, which we’ll get more into later. But it’s important to distinguish an allergyfrom a sensitivity or an intolerance, which involve uncomfortable symptoms as a reactionto 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 allergyresearch. In order to understand food allergies, weneed to know how the body evaluates food in the first place. In a typical immune system, your body is constantlyevaluating 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 notfight this in the future. So that every time they eat a peanut, theirimmune system does not react to it at all. The immune system is basically building upa tolerance for the next time peanuts are around.
But in the allergy afflicted, by the timethey 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 regulatorycells. 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 inflammatorycells to fight what they perceive as danger. In most people, the T regulatory cells holdmore 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 harmlessproteins on foods, most commonly milk, eggs, wheat, soy, peanuts, tree nuts, fish, or shellfish. But having a skewed immune system isn’tenough, there has to be a trigger point to developing a specific allergy, and that’sstill 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 aircan enter the body through the skin if there is dysfunction in the skin barrier due tosomething like eczema. We're talking about nanoparticlesof peanuts.
So it can be in your bedding, it can be inthe air. You might be getting exposed to it withoutany knowledge of it. It's that it's entering our, it's interacting with our immunesystem in a way that it's not meant to. We're not supposed to get food allergens tocome 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 theskin encounter these antigens, they recognize that they are foreign and in the wrong place. This ultimately signals the immune systemto produce antibodies called immunoglobin E or IgEs to fight against the food proteins.
Now, when this same food is finally ingestedthe right way through the mouth, the body’s IgE’s will recognize it as a threat andrespond in full force, leading to an allergic reaction. And the way this looks is basically, whenyour mast cells and basophils open up, they contain histamine and tryptase, and tryptaseand a bunch of other inflammatory mediators.
And those are what drives the reaction. This inflammatory response mirrors the body’sreaction 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 hopingto prevent.
We know that our immune system has developedthis kind of response, but we don't know the why. There is a genetic component to who has allergiesand who doesn’t. Children whose parents have allergies aremore likely to have allergies themselves. But there are other environmental factorsat 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'smodern 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 hypothesiswhich says that a lack of exposure to germs early in life can trigger the immune systemto mistake a food protein as an invading germ. So for fewer allergies, maybe... Get a dog, roll around in dirt, don't washyour clothes, and play in the sun.