55 Amazing Things Your Body Does to Protect Itself
Sneezing, sleeping, and craving food are all ways the body protects itself.
Between all the aches and illnesses of everyday life, it can seem like your body is failing you more often than not. But, in reality, that couldn't be further from the truth. In fact, those very pains and sniffles are proof that your body is your greatest protector. From regulating the temperature of your organs to flushing out bacteria from your ears and eyes, your body is constantly working to keep you in tip-top shape. Curious to learn more about the ways your eyelashes and even your toenails are keeping you healthy? Read on for 55 amazing ways the body protects itself.
Yawns to regulate brain temperature
Yawning isn't just a not-so-subtle signal to your friend that their story is boring you. This natural bodily inclination actually helps to regulate the temperature of your brain, according to the experts at the Smithsonian Institute.
"When we stretch our jaws, we increase the rate of blood flow to the skull," they note. "And as we inhale at the same time, the air changes the temperature of that blood flow, bringing cooler blood to the brain." And given how much work the brain does each and every day, this is a very important—and protective—function.
"Freezes" the brain to say "slow down"
An ice cream headache—also known as "brain freeze"—may be annoying, but it happens for a reason. According to 2013 research out of Wake Forest Baptist Medical Center, a brain freeze is your body's way of slamming on the brakes, letting you know you should slow down with whatever you're consuming.
"One thing the brain doesn't like is for things to change, and brain freeze is a mechanism to prevent you from doing that," Wake Forest Baptist Medical Center neuroscientist Dr. Dwayne Godwin explained in a statement.
Creates histamines to attack a mosquito's saliva
After you get a mosquito bite, it starts to itch—a lot. That's your body's way of taking action to help protect you from the bug's saliva.
Following the bite, your body identifies the bug's saliva as a foreign invader. "When a mosquito bites us, our body's immune system creates histamines, causing the skin around the mosquito bite to itch," explains Dr. Renee Matthews of Chicago, Illinois. "Your lymphocytes [a type of white blood cell] will go to where the bug bite is to try and kill the saliva off," adds Dr. Christopher Hollingsworth of NYC Surgical Associates. "This is then why your body creates a swelling bump that is itchy."
Uses the nose as a de facto air filter
Your nose doesn't just give your face some character—it's also your own personal built-in air filter. "Our nose is a filter that keeps many irritants out of our sinuses," explains Dr. Thomas Horowitz of CHA Hollywood Presbyterian Medical Center in Los Angeles, California. "The nose has mucus and hairs. The hairs filter larger particles and the mucus catches smaller ones."
Sneezes to clear foreign material
Sneezing is essential for good health. "The reason we sneeze is to clear our nasal passage from things like allergens and microorganisms," says Dr. Anthony Kouri, an orthopedic surgeon at the University of Toledo Medical Center in Toledo, Ohio. "This protects our bodies from many foreign materials."
When something foreign enters your nose, a signal is sent to the brainstem to close your throat, eyes, and mouth. Then, your chest tightens and your throat relaxes, causing your to expel the foreign material.
Gains weight during pregnancy to dilute chemicals, protecting the fetus
Though doctors advise only gaining a healthy amount of weight during pregnancy, putting on a few extra pounds can help protect the fetus from chemicals, according to a 2014 study published in the journal Environmental Health Perspectives. "Sufficient weight gain during pregnancy may help to dilute certain chemicals that store in fat, reducing exposure to the fetus," Dr. Jonathan Chevrier, an epidemiologist at McGill University, told Scientific American.
Boosts babies' immune systems through breastfeeding
Though breastfeeding is a completely personal choice, it does come with a few impressive health benefits. One of them is that it boosts a baby's immune system development, making the child less susceptible to allergies and asthma, according to 2015 research out of the Henry Ford Health System.
"For years now, we've always thought that a sterile environment was not good for babies. Our research shows why," Dr. Christine Cole Johnson, chair of Henry Ford's Department of Public Health Sciences and principal research investigator of the study, said in a statement. "Exposure to these microorganisms, or bacteria, in the first few months after birth actually help stimulate the immune system."
Grows eyelashes to protect eyes from foreign material
Eyelashes serve to shield your eyes from dust, sand, moisture and other debris in the air. "They also sense when something is too close to the eyes, triggering your blink reflex so nothing gets into your eyes—such as a flying insect," says Dr. Melody Huang, a Los Angeles-based optometrist.
And develops eyelids to do the same
Eyelids reflexively close quickly to form a mechanical barrier that protects the eyes from foreign material. "This can be triggered by the sight of something coming toward us or by the sensation of material on the eye," Kouri says. "Blinking also helps to flush out any debris into your puncta, which is the small opening in your eyelid where your tears drain out," Huang adds.
Creates tears to clean the eyes
Tears protect your eyes from getting infected by the teeny tiny things that manage to get past your eyelids and lashes. "They trap and whisk away small particles from the eye," Kouri explains. "Tears are also rich in antibodies, so they help protect the eye from infection."
He adds that "the eyelids also help spread tears across the surface of the eye." According to Huang, this helps your cornea stay moist, which is essential to maintaining clear vision.
Indicates disease via the sclera
The sclera is an extremely tough and fibrous tissue that protects the internal structures of the eye, Huang explains. "Not only does the sclera provide physical protection, but it's also an indicator of potential health problems," she says. "For example, in patients who have certain liver diseases, you may see a yellowing of the sclera known as jaundice."
Grows eyebrows to prevent sweat from getting in your eyes
Believe it or not, eyebrows do more than help frame your face: They prevent sweat, water, and other moisture from running into the eyes, Huang says. "The unique arched shape of our eyebrows allows moisture to run towards the side of your face rather than directly downwards into your eyes."
Sweats to keep you cool
Your skin plays a very important role in regulating your body's temperature. "It also allows us to sense the world around us," Kouri says. "For instance, if we could not feel the heat from a hot stove and reflexively pull away, we would severely injure ourselves."
In addition, the skin has various physiological roles. One you're surely familiar with—sweating—prevents you from overheating.
And to minimize inflammation
If you've ever woken up in a hot or cold sweat, it may be your body trying to tell you something serious. "I have had many patients come in complaining of excessive sweating and/or night sweats in response to a severe gluten intolerance or celiac disease," says Dr. Kristine Blanche, CEO of Integrative Healing Center in Northport, New York. "The exposure to gluten in these patients caused an inflammatory cascade of heat in the body." The sweating is the body's attempt to cool the inflammation and also to detoxify what the body thinks is poison, Blanche explains.
Burns up a fever to let you know you're sick
Your body has several built-in warning systems to let you know when something is off. One of the most common? A fever. According to the Mayo Clinic, a fever is a sign that there is something out of the ordinary with your body.
Fevers aren't cause for concern in adults, unless your temperature goes above 103 degrees Fahrenheit. In that case, head to a doctor, stat!
Forces you to sleep more when you're sick
When you're not feeling well, you may find yourself wanting to sleep all the time—and that's completely normal. In fact, it's your body's way of healing itself.
According to the Better Sleep Council, our bodies are more efficient at getting rid of unwanted germs and viruses while we're asleep. So, if you're at home while you're sick and start nodding off, don't fight the sleep—sleep to fight the illness.
Shivers to reduce internal temperature
If you have a fever and start shivering, that's your body attempting to regulate your internal temperature. When you shiver during a fever, your body is trying to raise its temperature, which may help fight infection by speeding up white blood cell production and slowing down bacteria reproduction, according to the BBC's Science Focus magazine.
Produces cortisol to trigger fight-or-flight
We usually think of cortisol—the stress hormone—as unequivocally bad for us, but it does serve an important function. When your body perceives a threat, your cortisol levels increase as your fight-or-flight response kicks in to help you deal with whatever may be dangerous, according to the Mayo Clinic. (Though nature says a "threat" would be, say, a charging wildcat, centuries-long nurture means, today, it's more likely going to be something like a suspicious person in your neighborhood.)
Of course, too much cortisol isn't great (hello, anxiety), but it does help protect you.
Develops goosebumps to stay warm
Goosebumps also serve as part of the human body's fight-or-flight response. "Goosebumps are a physiological phenomenon inherited from our animal ancestors," Dr. George A. Bubenik, a physiologist and professor of zoology at the University of Guelph in Ontario, told Scientific American. "In animals with a thick hair coat this rising of hair expands the layer of air that serves as insulation. The thicker the hair layer, the more heat is retained." In humans, this reaction is less helpful since we're less hairy—but the protective intention is there.
Swells up to raise the alarm about an injury
Swelling is the result of the increased movement of fluid and white blood cells into the area of inflammation after some sort of injury or during an illness, note the experts at Nationwide Children's Hospital. So, if you experience swollen hands, fingers, feet, legs or other body parts, it could be a sign that that body part requires medical attention, according to the University of Pennsylvania Medical Center.
And sends pain as a signal, too
When your body wants you to know something is wrong, pain acts as its alarm system. But the brain can regulate that pain, too. "New research shows that the body even has systems to ignore pain if there's something more exciting going on. The brain knows that if you're happy and paying attention to something, the pain alarm can't really be that dangerous, so it suppresses feeling pain," says Amy Baxter, MD, CEO and chief medical officer of Pain Care Labs. "In many ways, pain is just the body's opinion of how safe you are."
Swells up your tongue to signal an allergic reaction
Food allergies can be very serious—but luckily, our tongues give us a clue if something is wrong. A swollen tongue is an early sign that you should stop consuming whatever it is you've put in your mouth to avoid any further harm. As a 2008 study published in the Journal of Medical Case Reports notes, "allergic reactions often cause swelling in the tongue, which is usually more frightening than dangerous."
Creates layers of mucus to break down pathogens
Most of our body openings are protected by a layer of mucus. "Mucus not only moisturizes these openings, but also serves as an immune barrier equipped with enzymes to break down foreign pathogens," says Dr. Lindsey Elmore, a New York-based chemist, pharmacist, and board-certified pharmacotherapy specialist.
Internally cleans your respiratory system
The insides of your cells come equipped with tiny hairs known as cilia. "Cilia act as a sweep through the respiratory system, and help to clean out dust, debris, and pollutants," explains Elmore. "Cilia work in concert with mucus, which can help trap the dust so the cilia can brush the dirt-laden mucus out of the lungs."
Coughs to purge bacteria and allergens
Coughing may be a symptom of a cold or other illness, but it also is your body's way of getting rid of foreign particles, irritants, microbes, allergens, and bacteria. According to Doctor Doctor, coughing works by "forcing air out of the lungs under high pressure" and "attempts to clear the throat of these foreign particles."
Creates skin to protect against, well, everything
The skin is a flexible outer covering that acts as the body's first line of defense, Kouri explains. It protects you from harmful things like moisture, cold, heat, and pathogens. Not only that, but, according to Elmore, it also shields the body from mechanical impact and pressure, radiation, and chemicals.
Scabs over wounds to create new skin
When you cut or scrape your skin, you probably bleed for a bit before noticing some time later that a scab has formed over your wound. This protective tissue acts as a barrier against germs and keeps your cut covered as it heals, according to Healthline. Eventually, your skin will regenerate, pushing the scab off to make room for a new, healthy epidermis.
Protects the skin by making you feel itchy
When we feel something itchy, our instinct is to scratch that part of our body. This is actually an evolutionary response, initially developed to help animals remove parasites from their skin, according to the American Academy of Allergy, Asthma and Immunology.
Though we're less at risk of parasites these days, we still instinctively respond to even the slightest movement of hairs as a precautionary measure. Better safe than sorry!
Grows pubic hair to battle bacteria
Pubic hair is there for a reason: to provide "a protective barrier for our body," Dr. Jessica Shepherd, an OB-GYN at Baylor University Medical Center in Dallas, Texas, told Health. "It helps to fend off bacteria and unwanted pathogens from entering the vaginal area. This can help prevent you from getting yeast infections, vaginitis, and UTIs."
Produces loose stool to clear the gut
When you eat or drink something questionable, your body has its ways of flushing it out. "To many travelers' chagrin—that bout of 'Montezuma's revenge'—clears pathogens out of the gut fairly effectively," says Horowitz. "Diarrhea washes out the 'bugs' so they cannot colonize the gut."
Causes vomiting to purge parasites
When you eat or drink something contaminated, vomiting helps your body get rid of the bacteria, viruses, and parasites that are the root of the problem. According to the Mayo Clinic, food poisoning symptoms—like vomiting and diarrhea—typically start within hours of eating or drinking contaminated food, and they usually go away on their own.
Creates stomach acid to eliminate food-borne pathogens
It may not seem obvious, but stomach acid also serves as a protective substance in the body, Elmore explains, as it's able to kill food-borne pathogens. According to a 2003 study published in the Journal of Food Protection, "the secretion of hydrochloric acid by the stomach plays an important role in protecting the body against pathogens ingested with food or water."
Burps to release air from the stomach
Burping may be considered rude, but it also has a physiological purpose: It helps release excess air from your stomach. When air builds up in your upper stomach, it causes the organ to stretch. "This triggers the muscle at the lower end of the esophagus (the tube that runs from your mouth to the stomach) to relax," according to MedlinePlus. "Air is allowed to escape up the esophagus and out the mouth."
Flatulates to let excess air out
Though audible flatulence may be embarrassing, farting actually serves the same purpose that burping does. As LiveScience explains, gas forms in your intestines during the digestion process, and it gets trapped in your body every time you swallow something. That gas needs somewhere to go, and so the body releases it via (sometimes unpleasantly fragrant) flatulence and belches.
Develops calluses to protect skin
Calluses on your hands or feet form as your body's way of protecting your skin. "Calluses can develop anywhere on the body where there is repeated friction, such as a guitar player's fingertips or a mechanic's palms," board-certified dermatologist Dr. Nada Elbuluk, assistant professor of dermatology at NYU Langone Medical Center, explained to the American Academy of Dermatology.
Fills blisters with serum to help heal wounded skin
After breaking in a new pair of shoes or spending a day hiking, it's a good bet you'll end up with a few blisters. But though they can be painful and unpleasant, they're actually pretty helpful.
According to Harvard Medical School, the serum—that's the clear, watery liquid inside a blister—leaks in from neighboring tissues as a reaction to injured skin. If the blister doesn't pop, the serum can provide natural protection for the skin beneath it and help it heal.
Grows toenails to protect your toes
Your feet take a beating every day, but thanks to your toenails, the tops of your toes are protected. "They're made from keratin, which is the same protein that makes up your skin, hair, and fingernails," according to Healthline. "It's keratin that makes them tough and resilient to daily wear and tear."
Indicates disease via fingernails
Not only do fingernails protect the soft skin on the tops of your fingers, but they also serve as indicators of your health. For example, as pathologist Dr. Monisha Bhanote told SheKnows, rippled or pitted nails may be an early indicator of inflammatory arthritis or psoriasis. And yellow nails could mean more than a fungal infection; they could also be a sign of liver or kidney disease.
Inflames as a signal to eat healthier
As the body processes the nutrients from the food we eat, it detects refined carbohydrates and sugar and "responds with inflammation," says Lisa Richards, a nutritionist and the creator of The Candida Diet. "This is a protective mechanism as the body works to fight off these nutrients that it detects as harmful. Unfortunately, chronic consumption of this type of diet leads to chronic inflammation, which ultimately leads to poor health outcomes."
And to alert the immune system to start the healing process
The whole process of the immune system is also enhanced by inflammation. "The redness and swelling is actually there to protect you, as this signals to the immune system that repair and healing is needed," Elmore explains.
Eradicates infection via white blood cells
White blood cells known as phagocytes target infected cells and kill them off. "When exposed to an allergen, antibodies spring into action," Elmore explains. "They recognize foreign cells and bind to them and signal to the phagocytes that they need to die." Some antibodies last a lifetime and will permanently prevent infection—which is the case for people who have had chickenpox.
Fights off most viruses before they make you sick
Our bodies are attacked by all different kinds of bugs and viruses every day. However, you'll only get sick a few times a year, since your immune system naturally fights off these viruses. "Our immune system is made up of all different types of cells, organs, and tissues," says Jocelyn Nadua, a care coordinator at C-Care Health Services in Toronto. "These components instinctively recognize the dangers that approach our body and assures that it'll not be affected."
Injects melatonin into the brain to protect against neurodegenerative diseases
According to Richard L. Hansler, PhD, author of Parkinson's Disease: Evidence That Avoiding Blue Light Before Bedtime May Delay/Avoid Onset of the Symptoms, the pineal gland injects melatonin directly into the brain to protect against Alzheimer's, Parkinson's, and other neurodegenerative diseases. This hormone, which also regulates your sleep-wake cycle, "reverses the low degree inflammatory damage seen in neurodegenerative disorders and aging," notes Daniel P. Cardinali, MD, a professor of medical sciences at Pontificia Universidad Católica Argentina in Buenos Aires, Argentina.
Causes limbs to go numb to warn of a lack of blood flow
When you stay in the same position for a long period of time, it's likely you begin to experience numbness in that area of the body. "This is a warning from your body that your nerves are not getting the blood flow they need," Kouri says. "As a result, we should move from that position to prevent damage to the nerve or limb."
Creates tooth enamel to defend against decay
As the hardest substance in the human body, tooth enamel contains a high percentage of minerals. These minerals provide enamel with the strength it needs to protect the teeth and act as the body's first line of defense against tooth decay, explains Dr. Daniel Naysan of Bedford Dental Group in Beverly Hills, California.
Builds up earwax to shield ear canals from foreign objects
Though you may be in the habit of cleaning the earwax out of your ears after a shower, it's actually there to serve an important function. According to the Cleveland Clinic, earwax, also called cerumen, is made by the body to protect the ears, and has both lubricating and antibacterial properties.
Uses inner ears for balance
According to the Mayo Clinic, tiny particles called otoconia in your inner ear help monitor the position of your head in relation to gravity and linear motion, like when you're going up and down in an elevator. So, thanks to our inner ears, we're able to walk upright without getting too dizzy.
Chaps lips to warn of dehydration
Though several things can cause chapped lips, one of the main reasons you get them is because of dehydration. According to the University of Pennsylvania Medical Center, "when your body is dehydrated, your lips are more prone to dryness."
To help prevent chapped lips, drink about eight eight-ounce glasses of water each day.
Signals dehydration via headaches
Sometimes headaches are your body's way of telling you that you're dehydrated, according to the National Headache Foundation. If you've ever popped an aspirin and then downed a glass of water to swallow the pill, it's quite possible that you needed the fluid more than the medicine.
Removes bacteria from the bloodstream via the liver
The liver performs more than 500 distinct functions, according to Johns Hopkins University—and many of them help to protect the body, including resisting infections by removing bacteria from the bloodstream.
Removes waste via the kidneys
Like the liver, your kidneys also perform a variety of important functions, including removing waste products and excess fluid from the body via urine, according to the National Kidney Foundation.
Signifies heart problems via bedroom issues
Believe it or not, erectile dysfunction can serve a very important function: acting as a warning sign of current or future heart problems. That's because, as former executive editor of Harvard Health Publishing Patrick J. Skerrett notes: "From a purely mechanical perspective, an erection is a hydraulic event—extra blood must be delivered to the penis, kept there for a while, then drained away. An erection may not happen if something interferes with blood flow to the penis. That something is often atherosclerosis, the artery-clogging process at the root of most angina (chest pain with exercise or stress), heart attacks, strokes, and other cardiovascular conditions."
Offers vital information via vital signs
Vital signs are vital for a reason: They alert you if your basic bodily functions are normal or not. Your pulse is one of these vitals signs and all you have to do is use your fingertips to detect a beat in your neck or on your wrist. The normal pulse for healthy adults is between 60 to 100 beats per minute, according to Johns Hopkins Medicine, but that may fluctuate due to exercise, illness, injury, or emotional distress.
Produces insulin to regulate blood sugar
We most commonly hear about insulin in the context of diabetes, when the body isn't producing enough of it. But insulin is a hormone we all need to function. As registered dietician Amy Hess-Fischl writes for EndocrineWeb, insulin performs the important function of regulating our blood sugar, preventing it from getting too high (hyperglycemia) or too low (hypoglycemia). That's why those with diabetes need to carefully and continuously monitor their insulin levels. According to Hess-Fischl, "Insulin is often described as a 'key,' which unlocks the cell to allow sugar to enter the cell and be used for energy."
Gives you cravings for the nutrients you need
Sometimes when you're craving a certain food, it means that you're missing some critical nutrients. For instance, if you can't stop thinking about eating oranges, you may have a vitamin C deficiency. Or if you crave a juicy steak, you may be low on iron. Of course, this isn't the case all the time, but it's always worth paying attention to your cravings—especially if there seems to be a persistent pattern.
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