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.
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.