Here’s What Happens to Your Body During Anaphylaxis

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According to the Centers for Disease Control and Prevention, allergies affect more than 50 million Americans every year—and anaphylaxis, the most severe allergic reaction, affects at least 1.6 percent of the general population [PDF]. Here’s the science of what happens to the body during anaphylactic shock.

ALLERGEN EXPOSURE

In a person with allergies, cells sometimes identify foreign but innocuous stimuli as major threats. Why some people are allergic to certain things while others are not is a mystery science hasn't yet solved, but we do know how it happens: through a process called sensitization.

Here’s how it works. When the body encounters a foreign substance, also called an antigen, immune system cells deliver some of substance's molecules to T-helper cells living in the lymph nodes. Those cells also bring along a type of molecule that informs a T-helper cell it’s time to stage an immune response. Known as a costimulatory molecule, it's necessary to activate any type of immune system reaction involving T cells, whether you have allergies or not.

Being exposed to an antigen "primes" a T-helper cell, turning it into a Th2 cell. Primed Th2 cells release proteins called interleukins, which do two things: First, they interact with another type of immune cell called B cells to produce infection-fighting antibodies that bind to mast cells, which contain chemical particles they'll release in the presence of an antigen. Second, the interleukins activate eosinophils, a type of white blood cell that discharges toxic substances to destroy invading cells (and, occasionally, host cells). In this process, the immune system identifies the "threat" and deploys cells prepared to fight it. The immune system's elevated level of awareness of and preparation against the antigen reclassifies the substance as an allergen—a considerably more dangerous threat.

Because an allergy only develops after this process, a person allergic to strawberries, for example, will only experience a reaction the next time they eat something containing strawberries. New allergies can pop up at any point in your life.

An immune system on allergies is a little bit like a brain that can't distinguish a piece of lint from a spider: unable to relax, constantly on guard against every potential threat. After initial exposure, the mast cells activated during the sensitization phase are still equipped with allergen-specific antibodies and remain combat-ready, prepared to respond immediately should a second exposure ever occur. If it does—and it probably will—here’s what you can expect to happen.

ALLERGIC REACTION

If two or more allergen molecules bind to a sensitized mast cell, the mast cell releases inflammatory mediators that produce an allergic reaction. These mediators include substances like histamine and more of the interleukins that, in turn, activate eosinophils, Th2 cells, and basophils (another type of white blood cell). In a non-allergic reaction, mediators produce helpful inflammation that prevents infection and initiates healing—but those same symptoms can be annoying and even dangerous when the immune system attacks an otherwise benign allergen. Mast cells also release leukotrienes, which recruit more immune cells to the area and speed up the reaction. That leads to what Stanford University researcher Tina Sindher calls a “‘chain reaction’ of allergic inflammation.”

With the release of histamine, you might experience both bronchial contraction—which makes it more difficult to breathe—and blood vessel dilation. The latter makes it easier for blood to flow to affected areas, but it also makes blood vessels more permeable, allowing blood to escape from the blood vessel walls and flow into the spaces between cells and causing swelling and hives.

For most, these symptoms are merely uncomfortable; they can occur as late as eight to 12 hours after initial exposure, long after the allergen is gone, and can be alleviated with an antihistamine like Benadryl. But for a person with severe allergies, a life-threatening allergic response can occur within minutes: Their airways will constrict so much they won't be able to breathe, and their blood vessels will be unable to contract, which can lead to a drop in a blood pressure and keep veins from getting blood back to the heart. The combination of airway constriction and blood vessel dilation can make it impossible for the body to supply enough oxygen to major organs—that's anaphylactic shock.

The only way to stop anaphylaxis in its tracks is with epinephrine, more commonly known as adrenaline. Adrenaline is a hormone naturally produced by the adrenal glands to help generate the "fight or flight" response in emergency situations. It works by constricting certain blood vessels, increasing blood pressure, and relaxing airways, counteracting all the reactions produced by histamines.

According to Sindher, it’s important to use epinephrine immediately if you're at risk for anaphylactic shock. “There’s a general belief out there that epinephrine should only be used in the worst-case scenario,” she tells Mental Floss. “In fact, most of the complications we see in food allergic reactions are due to delayed use in Epi. Antihistamines can be helpful in treating the symptoms of itching and congestion, but they do not help stop an allergic reaction.”

THE FUTURE OF ALLERGY TREATMENT

Researchers like Sindher are still trying to understand what causes allergies, and why the prevalence of food allergies has increased over the past few decades. Sindher’s main goal is to find new ways of treating (and hopefully curing) allergies. The most established technique (for food allergies, at least) is oral immunotherapy, where allergic individuals gradually eat more of their allergen until they can have small amounts without experiencing a reaction. That’s usually done extremely gradually, over the course of months or years, and always under the supervision of a certified allergist.

image of two epipens sitting on a desk
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Sindher says scientists are still testing other types of immunotherapy treatments and vaccinations in clinical trials: “A lot of research is going into trying to identify the causes so we can be successful in the prevention as well as treatment of food allergies.”

Until that happens, though, doctors say the best course of action is to be careful around allergens. Medications are useful and necessary, but prevention is the name of the game when it comes to allergies.

Now Ear This: A New App Can Detect a Child's Ear Infection

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iStock.com/Techin24

Generally speaking, using an internet connection to diagnose a medical condition is rarely recommended. But technology is getting better at outpacing skepticism over handheld devices guiding decisions and suggesting treatment relating to health care. The most recent example is an app that promises to identify one of the key symptoms of ear infections in kids.

The Associated Press reports that researchers at the University of Washington are close to finalizing an app that would allow a parent to assess whether or not their child has an ear infection using their phone, some paper, and some soft noises. A small piece of paper is folded into a funnel shape and inserted into the ear canal to focus the app's sounds (which resemble bird chirps) toward the child’s ear. The app measures sound waves bouncing off the eardrum. If pus or fluid is present, the sound waves will be altered, indicating a possible infection. The parent would then receive a text from the app notifying them of the presence of buildup in the middle ear.

The University of Washington tested the efficacy of the app by evaluating roughly 50 patients scheduled to undergo ear surgery at Seattle Children’s Hospital. The app was able to identify fluid in patients' ears about 85 percent of the time. That’s roughly as well as traditional exams, which involve visual identification as well as specialized acoustic devices.

While the system looks promising, not all cases of fluid in the ear are the result of infections or require medical attention. Parents would need to evaluate other symptoms, such as fever, if they intend to use the app to decide whether or not to seek medical attention. It may prove most beneficial in children with persistent fluid accumulation, a condition that needs to be monitored over the course of months when deciding whether a drain tube needs to be placed. Checking for fluid at home would save both time and money compared to repeated visits to a physician.

The app does not yet have Food and Drug Administration (FDA) approval and there is no timetable for when it might be commercially available. If it passes muster, it would join a number of FDA-approved “smart” medical diagnostic tools, including the AliveKor CardiaBand for the Apple Watch, which conducts EKG monitoring for heart irregularities.

[h/t WGRZ]

Does Having Allergies Mean That You Have A Decreased Immunity?

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iStock.com/PeopleImages

Tirumalai Kamala:

No, allergy isn't a sign of decreased immunity. It is a specific type of immune dysregulation. Autoimmunity, inflammatory disorders such as IBS and IBD, and even cancer are examples of other types of immune dysregulation.

Quality and target of immune responses and not their strength is the core issue in allergy. Let's see how.

—Allergens—substances known to induce allergy—are common. Some such as house dust mite and pollen are even ubiquitous.
—Everyone is exposed to allergens yet only a relative handful are clinically diagnosed with allergy.
—Thus allergens don't inherently trigger allergy. They can but only in those predisposed to allergy, not in everyone.
—Each allergic person makes pathological immune responses to not all but to only one or a few structurally related allergens while the non-allergic don't.
—Those diagnosed with allergy aren't necessarily more susceptible to other diseases.

If the immune response of each allergic person is selectively distorted when responding to specific allergens, what makes someone allergic? Obviously a mix of genetic and environmental factors.

[The] thing is allergy prevalence has spiked in recent decades, especially in developed countries, [which is] too short a time period for purely genetic mutation-based changes to be the sole cause, since that would take multiple generations to have such a population-wide effect. That tilts the balance towards environmental change, but what specifically?

Starting in the 1960s, epidemiologists began reporting a link between infections and allergy—[the] more infections in childhood, [the] less the allergy risk [this is called hygiene hypothesis]. Back then, microbiota weren't even a consideration but now we have learned better, so the hygiene hypothesis has expanded to include them.

Essentially, the idea is that the current Western style of living that rapidly developed over the 20th century fundamentally and dramatically reduced lifetime, and, crucially, early life exposure to environmental microorganisms, many of which would have normally become part of an individual's gut microbiota after they were born.

How could gut microbiota composition changes lead to selective allergies in specific individuals? Genetic predisposition should be taken as a given. However, natural history suggests that such predisposition transitioned to a full fledged clinical condition much more rarely in times past.

Let's briefly consider how that equation might have fundamentally changed in recent times. Consider indoor sanitation, piped chlorinated water, C-sections, milk formula, ultra-processed foods, lack of regular contact with farm animals (as a surrogate for nature) and profligate, ubiquitous, even excessive use of antimicrobial products such as antibiotics, to name just a few important factors.

Though some of these were beneficial in their own way, epidemiological data now suggests that such innovations in living conditions also disrupted the intimate association with the natural world that had been the norm for human societies since time immemorial. In the process such dramatic changes appear to have profoundly reduced human gut microbiota diversity among many, mostly in developed countries.

Unbeknownst to us, an epidemic of absence*, as Moises Velasquez-Manoff evocatively puts it, has thus been invisibly taking place across many human societies over the 20th century in lock-step with specific changes in living standards.

Such sudden and profound reduction in gut microbiota diversity thus emerges as the trigger that flips the normally hidden predisposition in some into clinically overt allergy. Actual mechanics of the process remain the subject of active research.

We (my colleague and I) propose a novel predictive mechanism for how disruption of regulatory T cell** function serves as the decisive and non-negotiable link between loss of specific microbiota and inflammatory disorders such as allergies. Time (and supporting data) will tell if we are right.

* An Epidemic of Absence: A New Way of Understanding Allergies and Autoimmune Diseases Reprint, Moises Velasquez-Manoff

** a small indispensable subset of CD4+ T cells.

This post originally appeared on Quora. Click here to view.

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