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.

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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.

A Custom Wheelchair Allowed This Brain-Injured Baby Raccoon to Walk Again

фотограф/iStock via Getty Images
фотограф/iStock via Getty Images

Animal prosthetics and wheelchairs allow dogs, cats, and even zoo animals with limited mobility to walk again, but wild animals with disabilities aren't usually as lucky. Vittles, a baby raccoon rescued in Arkansas, is the rare example of an animal that was severely injured in its natural habitat getting a second shot at life.

As Tribune Media Wire reports, Vittles came to wildlife rehab specialist Susan Curtis, who works closely with raccoons for the state of Arkansas, with a traumatic brain injury at just 8 weeks old. The cause of the trauma wasn't clear, but it was obvious that the raccoon wouldn't be able to survive on her own if returned to the wild.

Curtis partnered with the pet mobility gear company Walkin' Pets to get Vittles back on her feet. They built her a tiny custom wheelchair to give her balance and support as she learned to get around on her own. The video below shows Vittles using her legs and navigating spaces with help from the chair and guidance from her caretaker.

Vittles will likely never recover fully, but now that she's able to exercise her leg muscles, her chance at one day moving around independently is greater than it would have been otherwise. She now lives with her caretaker Susan and a 10-year old raccoon with cerebral palsy named Beetlejuice. After she's rehabilitated, the plan is to one day make her part of Arkansas's educational wildlife program.

[h/t Tribune Media Wire]

Why You Should Never Shower With Your Contact Lenses In

belchonock/iStock via Getty Images
belchonock/iStock via Getty Images

Contact lenses offer a level of convenience for those with less-than-perfect vision that glasses can hardly compete with, but that doesn’t mean the daily struggle of taking them in and out of your eyes doesn’t wear on you. If you get a little lazy and decide it’s fine to leave them in your eyes during showers or pool parties, think again.

According to Popular Science, a 41-year-old woman in the UK lost sight in her left eye as a result of frequently showering and swimming without removing her contacts. The culprit was Acanthamoeba polyphaga, a protozoa that crawled into her eye and caused a cornea infection called Acanthamoeba keratitis. After two months of pain, blurry vision, and light sensitivity, the woman sought medical attention at the Manchester Royal Eye Hospital, where doctors discovered a ring shape in her left eye and a hazy layer covering her cornea. Upon testing her vision, they found that her left eye was now 20/200, which counts as legally blind in the United States.

Leela Raju, an ophthalmologist and cornea specialist at New York University, told Popular Science that the single-celled organisms “can be anywhere,” including pools, hot tubs, showers, dirty saline solution containers, and even tap water. Lens-wearers make up around 85 percent of those who get infected, and experts think it may be because the amoeba can latch onto a contact lens more easily than a bare eye.

Though Popular Science reports that Acanthamoeba keratitis only affects one or two people out of every million contact wearers each year, that’s no reason not to be careful. If you do catch it, you’ll likely need a cornea transplant, and even that won’t necessarily restore your eyesight to its previous state—after her transplant, the UK woman’s left eye now has 20/80 vision.

“It’s just a long road, for something that’s totally preventable,” Raju says. In addition to removing your contacts before swimming, showering, or sleeping, you should also refrain from reusing saline solution, make sure your contact case is completely clean and dry before filling it with more solution, and check out these other tips.

[h/t Popular Science]

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