Grossology: The Science of the Disgusting

Kids and adults learn how and why the body does those yucky things it does - like pooping, farting, belching, and making snot.

Medically Reviewed by Brunilda Nazario, MD

"Sometimes it's stinky. Sometimes it's crusty. And sometimes it's slimy. But hey, it's your body," writes Sylvia Branzei, author of the book, Grossology: The Science of Really Gross Things.

The book has become a cultural phenomenon, translated into Japanese, Korean, Bulgarian, Spanish, and French. A Grossology museum exhibition is also touring; it's an interactive biology lesson featuring boogers, burps, poop, snot, scabs, spit, farts, and body odors.

"I realized a long time ago that you have to get kids' attention, and children have an affinity for disgusting stuff," says Branzei, who spent many years as a science teacher (kindergarten through high school) in California.

"The goal is really to teach science, not gross anybody out," Branzei tells WebMD. "But the grossness is definitely the hook."

Farts, after all, are cool to kids. "So is poop," Branzei notes. "I think I'm normal, but maybe not -- I always look at my poop. Yet one woman told me she never looks at hers. The take-home lesson is that what you excrete tells you whole lot about yourself and your diet. The color of what you excrete is super important. My poop and snot probably look different from other people's. People need a baseline ... they need to look at their stuff, so they can tell when it changes."

The exhibit and book focus on "the everyday disgusting stuff," she explains. "So it's the 'eeewww' factor combined with the 'this-is-familiar' factor - so we can teach anatomy and physiology and health science. The hope is that if they learn more about their bodies, then they'll be inclined to take better care of themselves."

"It's totally like the Fear Factor TV show, but with biology behind it," says Sharon Horesh, MD, instructor of clinical medicine at Emory University School of Medicine in Atlanta. "The best biology teacher teaches you things you remember, and always answers the 'why' questions ... the questions about biology that most people don't know the answers to."


"Puking is pretty important for your body," writes Branzei. "It gets rid of the stuff that your body thinks could be dangerous to you. In fact, throwing up is so important that there is part of the brain called the vomit center that causes this uncontrollable act. Once the vomit center goes into action, you cannot help but let loose."

Indeed, the act of vomiting has many triggers. It eliminates anything that bothers the stomach's lining - excess food or drink, poisonous substances, bacteria, or viruses. If your inner ear canal is unbalanced, as happens during sailing and driving, the brain's vomit center gets an alert. Hormone changes during early pregnancy trigger the vomit response. Anything unpleasant can prompt you to vomit.

"Those are the natural reactions," Horesh says. "They're either protective functions or body quirks."

However, chronic nausea and vomiting are symptoms of acid reflux disease (heartburn) -- a potentially serious health problem, she tells WebMD. Some people have chest pain or asthma caused by acid reflux, she adds.

"Most people with acid reflux think they have a nervous stomach, and try to modify their diet," Horesh explains. "But for many people, simply avoiding spicy food or marinara sauce isn't going to do enough... and taking Tums or Rolaids helps only a little. Newer medicines like Prilosec and Nexium, though, can prevent acid reflux from developing into a more serious problem."

Vomiting and nausea can also be symptoms of gallstone and gallbladder disease, which can be a diet-related problem, she adds.


Mucus (a.k.a. snot) is the sticky liquid that coats the skin and hairs in your nose. It has a special bacteria-killing chemical, and it also keeps junk from reaching your lungs, explains Branzei. "Snot is so important that your nose makes a new batch every 20 minutes."

Boogers are actually "nose garbage," she writes. "Each day, you suck in a small roomful of air. If the air was only gas, you would not even make boogers. But the air is filled with dust, smoke, grit, bacteria, tiny fungi, pollen, soot, little metal pieces, ash, fuzz, sand, and even itty bitty meteorites. One job of the nose is to clean the stuff out."

This nose-cleaning system is so effective that the nasal area is one of the cleanest parts of your body, Branzei adds. However, allergies and pollutants will trigger inflammation in the sinus lining, which creates sinus drainage, Horesh explains. "For some people, that means a runny nose, for other people, it's post-nasal drip."

Nasal sprays may help with post-nasal drip. Allergy shots and pills can control allergic reactions. "If air quality is a problem, another option is to move to Colorado," Horesh says.

Another tidbit: "The reason that smokers have more sinus and upper respiratory infections is because smoking damages the cilia, the hairs lining the sinus membranes which interfere with the natural snot mechanism," Horesh explains.

Farts & Gas

A fart is actually a mixture of gases in your large intestine. As bacteria accumulate around undigested food in your gut, they release gas, which builds in your intestine, explains Branzei.

Burping and belching are produced during the digestive process. As the stomach acids digest food, gas is created. When too much builds up, pressure builds, and gas seeks a means of escape. It often carries a food-related aroma like onions.

Some foods produce more gas than others: wheat products, dairy products, cabbage, apples, radishes, broccoli, onions, cauliflower, and (of course) beans. These are high-fiber, sugary foods that the body has trouble digesting.

Gas is rarely a serious problem, unless it's caused by acid reflux disease, says Horesh. "For people who are lactose intolerant - who can't digest dairy products - there is only short-term discomfort. For them, the worst thing that can happen is a nutritional deficiency if they always avoid dairy. But they're not damaging the intestines by eating dairy."

Sweat & Body Odor

"Smelly sweat comes from sweat glands located mostly in the armpits but also in the crotch, anus, and a little on the scalp," Branzei writes. Sweating is the body's air conditioning system. When sweat is released, it coats the skin to remove heat from the body. When sweat evaporates, you cool down. Salts and urea are left behind. That's why sweat tastes salty and feels sticky.

Until age 12 or so, sweat glands aren't active. That's why adults are so stinky and kids aren't, she explains. The sweat itself is actually not a problem; it's pretty much odorless. In fact, your palms have more than 2,000 sweat glands -- much more than any body part -- but they don't attract bacteria that cause bad smell.

Some foods like onions, garlic, curry -- and even some medications -- can give your sweat an extra scent, explains Horesh. Some physical changes can cause excess sweat, as happens with infections, menopause, anxiety, and overactive thyroid. "And the more you sweat, of course, the greater chance that bacteria on your skin will make you smell," she says.

Also, a diabetes-related problem called diabetic ketoacidosis can cause a sweet, slightly fruity -scented breath or skin smell, Horesh says.

Factoid: During the Middle Ages, bathing was not in style. Not having to bathe was a sign of wealth. They certainly did sweat and stink, however -- and covered it up with perfumes, oils, and spices.

Bad Breath

Almost everyone occasionally has bad breath (halitosis), Branzei writes. Bacteria cause "morning breath," which brushing will eliminate. Enzymes in onions and garlic cause their own special breath problems; enzymes get into the blood, which makes its way to your lungs, so you breathe flavored gas. Smokers' breath comes from smoke that contaminates the lungs.

When bad breath is a chronic problem and can't be eliminated with mints, mouthwash, brushing or avoiding onions, it may be a symptom of a different problem. Sinus infections, allergies, decaying teeth, diseased gums, and digestive problems are just a few reasons for chronic bad breath. It's time to check with a dentist or a doctor.

Post-nasal drip and acid reflux can cause bad breath, notes Horesh. As with sweating, diabetic ketoacidosis can also trigger a sweet, fruity smelling breath. "It's rare, but we do see it."

And while it's not a dangerous problem, something called "tonsiliths" or "tonsil stones" are fairly common, Horesh adds. "It's mucus mixed with natural mouth bacteria that forms a dime-sized collection that looks like cauliflower. It gets stuck in the roof with your tonsils, and you can cough it out. It looks really gross, but it's a natural phenomenon. It just freaks a lot of people out."

"These are all the things that doctors love to talk about," Horesh tells WebMD. "We think we've got a great story to tell at a party when we talk about a patient who was vomiting bile 3 feet out. Then when people start walking away we realize not everyone is comfortable hearing about these things."

Show Sources

SOURCES: Branzei, S. Grossology, Price Stern Sloan, 2002. Sylvia Branzei. Sharon Horesh, MD, instructor of clinical medicine, Emory University School of Medicine, Atlanta.

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