Here’s What Happens to Your Body During Anaphylaxis

iStock
iStock

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
iStock

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.

Nearly Half of American Adults Don't Know Their Own Blood Type

iStock.com/nzphotonz
iStock.com/nzphotonz

If you know your blood type, you’re better off than nearly half of Americans. Of the 1004 adults in the U.S. who answered a recent Quest Diagnostics survey, only 57 percent said they knew whether they have type A, B, AB, or O blood.

This is roughly the same number of people who could recall their childhood phone number (55 percent), the survey revealed. By comparison, 74 percent of respondents remembered their lengthy Wi-Fi password, and 75 percent knew how much money was in their bank account.

For many, other personal health information was even murkier. Fewer than two in five people knew their cholesterol or blood sugar levels. Considering that these details provide important insights into one’s risk for certain diseases, survey administrators said this is a cause for concern.

“With consumers increasingly engaged in their own and their loved ones’ health care, it’s critical that they ‘know their numbers’—and have those numbers readily accessible—to ensure productive communication with their healthcare provider for both routine and critical care,” Cathy Doherty of Quest Diagnostics said in a press release.

With the exception of emergencies, at which time you may receive a universal donor's O-negative blood, doctors will almost always conduct blood typing and cross-matching tests to determine your blood type and identify minor antigens in your blood before conducting a transfusion or surgery.

It’s still important to know your blood type for other reasons. Newborn babies, for example, can develop hemolytic disease if their Rh blood type (meaning whether it's positive or negative) doesn’t match their mother's. And depending on your blood type, you may also have an increased risk for blood clots, heart disease, certain types of cancer, and even severe diarrhea and mosquito bites.

If you know your blood type, you’re also in a better position to donate blood and help people in need if there’s a natural disease or emergency, or if blood banks simply have a low supply. O blood tends to be the highest in demand (and O-positive is the most common blood type), but blood banks may issue public notices from time to time if they need a particular type.

If you’re unsure of your blood type, clinical labs like Quest Diagnostics offer blood type tests. You can also order test kits online from Amazon.

Can Watching the Super Bowl Give You a Heart Attack?

iStock.com/skynesher
iStock.com/skynesher

With the clock nearing zero, the 2006 divisional round playoff between the Indianapolis Colts and the Pittsburgh Steelers looked to be over: It was the fourth quarter, with one minute and 20 seconds left, and the score was 21-18. Pittsburgh held the lead and, by all appearances, was about to score again.

Pittsburgh's offense lined up on the Indianapolis 2-yard line and handed the ball to future Hall of Fame running back Jerome Bettis, a cannonball of a man who famously went by the nickname "The Bus." Nearly everybody assumed Bettis would pound the ball through the goal line. Instead, Colts linebacker Gary Brackett forced a fumble. The Colts picked up the ball and nearly ran it back for a touchdown. For Steelers fans, it was a sudden and heartbreaking turn of events. Literally.

Watching from a bar, a diehard Steelers fan named Terry O'Neill watched the ball tumble to the ground and suddenly felt a pain in his chest. Luckily, two firefighters in the crowd helped resuscitate him.

"My heart just quit beating completely," O'Neill later told the South Pittsburgh Reporter. "For all intents and purposes, I died."

Research indicates he wasn't the first. Watching a high-stakes game could actually kill you.

A 2002 study in The BMJ, which focused on the health of English soccer fans, found that a "myocardial infarction can be triggered by emotional upset, such as watching your football team lose an important match." A 2008 study published in the New England Journal of Medicine followed the World Cup-watching habits of German soccer fans and found that watching a stressful game more than doubled viewers' chances of experiencing a cardiovascular event. A similar result was found when other researchers looked at cardiovascular deaths in the Netherlands after the country's soccer team lost the European soccer championships on a penalty shootout in 1996.

In 2011, a study published in Clinical Cardiology looked at the Super Bowl specifically and found that deaths increased after the big game in the losing city, finding an "absolute increase in all cause mortality" in people over the age of 65. The researchers argued:

"Acute risk factors usually involve some form of stress—physical, emotional, or both—that increase the sympathetic nervous system and releases catecholamines. The subsequent increase in heart rate, blood pressure, and ventricular contractility increase oxygen demand and may change the shear stress of blood against an atherosclerotic plaque, contributing to plaque fracture."

This particular study, however, has received some criticism. It only looked at mortality statistics for the 1980 and the 1984 Super Bowls, a relatively small sample. Some researchers said the study went too far in implying that the Super Bowl caused death, considering that the viewer's behavior and health history (and not the events of the game itself) could have been responsible. Super Bowl Sunday, after all, is a day filled with fatty fried foods and copious amounts of alcohol—all possible risk factors for a cardiovascular event.

As Gregg Fonarow, director of the Cardiomyopathy Center at UCLA, tells LiveScience, "It may be other behaviors associated with important sporting events rather than the stress of watching the home team lose that may explain these associations." Additionally, pre-existing conditions could be a huge contributing factor. (This was the case for our fateful Steelers fan.)

Study limitations aside, becoming invested in the outcome of a sporting match is undeniably stressful on the heart. A recent (though small) study out of Canada surveyed the heart rates of hockey fans during games, revealing "a mean increase of 92 per cent among the 20 test subjects, rising from an average rate of 60 to 114 beats per minute," according to the Montreal Gazette. In other words, people sitting and watching TV had heart rates equivalent to people undergoing mild exercise. Their heart rates only got higher when they watched games in person.

Of course, you don't have to do a study to learn that close games can cause a diehard fan's heart to pound—just go and ask one. And if they mutter, "This team is going to kill me!," kindly suggest that they step away from the TV before it becomes a self-fulfilling prophecy.

SECTIONS

arrow
LIVE SMARTER