If you have a cold, the body produces excess mucus to trap germs

Stuffy nose congestion occurs because of swelling of the inferior turbinates

These structures in the nose above the nose hairs swell and shrink constantly and are affected by head position. They can fill with blood during illness, causing the feeling of congestion, but also when a person changes position, especially when lying down. Medications can be used to shrink them, providing temporary relief.

The marvels of mucus

Mucus—otherwise known as snot or phlegm—has a gross reputation, but the substance is actually of vital importance, lining the moist surfaces of our nose, intestines, lungs, and more. It plays a constant role in keeping our tissues from drying out and acts as a line of defense, but if it gets too sticky or thick, it can cause problems. Read about the marvels of mucus here.

Nasal congestion is a common side effect of pregnancy, called pregnancy rhinitis

In one recent study, almost 100% of pregnant women experienced this condition in their third trimester. The congestion is likely due to hormonal changes and neurophysiological factors, and it may also worsen at night due to circadian factors and gravitational redistribution when lying down. Treatments include saline nasal irrigation and the use of nasal strips to widen the nasal valve area.

Nasal hairs, called vibrissae, help protect the body from particulate matter and other dirt

The nose structure plays a key role in filtering air before it enters our lungs and makes sure that the air temperature and humidity are also suitable for the body.

Why we don't have an answer for the common cold

Since a landmark study of the common cold in 1925, researchers have learned much more about the seasonal ailment. Despite continuous study, people still contract colds for similar periods of time at the same rate with the same symptoms, and there's no vaccine. This article explains how the many viral strains make it hard to control.

Inhalers dilate airways and reduce inflammation

People with asthma suffer from constricted airways in their lungs, whether from muscle pressure, mucus buildup, or inflammation. Inhalers help people breathe medicine directly into their lungs to immediately relieve these symptoms.

A closer look at why people snore

Snoring is simply noise caused by improper airflow during sleep—and while it’s something that most people will do at some point in their lives, it can also be indicative of larger health problems. Generally speaking, snoring occurs when soft...

Fevers are an immune response to create hurdles for pathogens

Substances called pyrogens prompt the brain to raise the body temperature to levels where bacteria and viruses struggle to survive. The higher temps also support immune cells fighting off the invaders.

This is what happens inside your body when you're sick

This video details the biology of what happens inside the human body during illness.

This decongestant doesn't work, so why is it still for sale?

Over-the-counter decongestants powered by phenylephrine won't help those with stuffy sinuses find relief, according to current evidence. This 10-minute video explores why these useless medications are still for sale in the US. The decongestant...

Cold water swimming can induce positive stress

The tradition of cold water swimming (or taking a cold plunge, or even a cold shower) has been shown to release the same hormones triggered during a stress response. This can have the effect of increasing blood flow, improved mental acuity, and more.

The history of germ theory, which explains that illnesses are caused by microorganisms

For centuries, the miasma theory, which held that illnesses were caused by clouds of "bad air" produced by decaying organic matter, was the accepted explanation for the spread of disease. The development of microscopes and the subsequent technology to isolate bacteria and test disease spread in mice greatly contributed to contagionists overturning miasmatists.

What is a sneeze? (And can it kill you?)

A sneeze is an important involuntary reflex to expel something that is irritating your nose. But can it kill you? No, say these silly video hosts. Although, the sneeze can expel air, saliva, and mucus at nearly 100 miles per hour in a five-foot radius. See them break it down with this quick, quirky video.

Surfer's ear, from repeated cold water exposure, leads to new bony protrusions in the ear

Frequent exposure to icy cold water, typical in surfing, can cause tiny bony growths to develop in the ear canal, informally called surfer's ear. While the exact cause for these growths is unknown, it may be the body's protective response to shield the ear drum from the cold. These protrusions can heighten the risk of swimmer's ear, lead to wax buildup, and result in hearing loss.

Broken or neglected air conditioners are risky for respiratory health

A well-maintained air conditioner can typically keep out unwanted pathogens, but units that are dusty or water-logged can foster germs and cause harm. AC units also remove moisture from the air, potentially causing mucus membranes to dry out and become vulnerable to infection.

When common sounds become disturbing

Misophonia causes certain sounds to feel violating, triggering a "very visceral kind of experience" filled with extremely unpleasant emotions, including annoyance, anger, and disgust. A 2017 study found that people with misophonia have elevated activity in the brain's anterior insula—a region associated with interoception, emotional processing, and behavioral responses—when exposed to trigger sounds. Ongoing research suggests trigger sound context affects the severity and manifestation of the condition.

Flu spreads through droplets in the air and on surfaces

Influenza passes mainly through tiny droplets released when sick people cough, sneeze or talk. The virus can also survive briefly on surfaces, allowing it to spread when others touch contaminated objects.

Sweat doesn't smell, but bacteria multiply in moist environments—and cause an odor

Body odor is associated with sweat, but odor actually arises from the bacteria that multiply in moist environments on your skin. Hormones, medications, food, and body hair can all affect body odor.

Cerebrospinal fluid flushes waste from your brain during sleep

Recent research suggests a nightly brain cleanup as an important purpose of sleep. Brain waves have been observed to work in lockstep with the brain’s blood flow and cerebrospinal fluid flow, allowing for a cleansing tide that washes away toxic waste.

Chronic inflammation can cause cellular damage and could lead to cancer

Over time, this cellular defense system can inadvertently damage cells and tissues when it's in this heightened alarm mode over a prolonged period. This occurs because, when immune cells are sent somewhere without a true target, they may attack healthy cells and tissues.

Increases in atmospheric carbon dioxide lead plants to produce more pollen

Pollen issues are emerging earlier in the year and lasting longer as rising levels of carbon dioxide in the atmosphere boost plants’ pollen production and also simultaneously extend warmer, pollen-producing seasons.

Bears have evolved natural mechanisms to avoid blood clots while hibernating

Movement is essential to keeping blood from clotting, which raises the question of why animals such as hibernating bears don't suffer from clots despite going months lying still. New research suggesting that the animals may have evolved to have lower concentrations of a specific protein may explain this phenomenon.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Instabilities in the polar jet stream can bring cold Arctic air southward

The polar jet stream marks the boundary between mid-latitude air and the much colder polar air, which are normally contained by the polar vortex—a ring of strong winds that circles the Arctic around 16 to 50 kilometers (10 to 30 miles) above the Earth's surface. Climate change may be responsible for "blocking patterns" that distort the jet stream, allowing polar air to leak into lower latitudes.

Herpangina is a related disease that also has characteristic sores in the mouth and throat

This painful condition is also caused by several viruses in the enterovirus family. The condition typically has early symptoms including a fever and sore throat, in addition to the sores. Herpangina is often mistaken for strep throat, but there's no cure for herpangina and patients typically have symptoms for about a week.

Eating too much salt can worsen vertigo

High salt intake can cause fluid retention in the inner ear, worsening vertigo. Slashing sodium amounts (and caffeine and alcohol consumption) are particularly recommended for those suffering from Ménière's disease to help stabilize inner ear fluid levels.

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Tattoos remain visible on your skin thanks to immune cells called macrophages

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

Some researchers have labeled nomophobia, the fear of being without your phone, as 'the phobia of the 21st century.'

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

The story of Dollree Mapp, whose legal challenge over her 1957 conviction for possessing "obscene material" led to a major strengthening of the Fourth Amendment

Poison ivy's characteristic rash is caused by an allergic response to an oily compound in the plant called urushiol.

'Grand Canyon of the Yellowstone,' a work by American painter Thomas Moran, inspired Congress to establish Yellowstone National Park.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

Waves off the coast of Nazaré, Portugal, can reach over 100 feet and are caused by the area's deep underwater canyon geography

Double world record holder Hunter Ewen helped conquer his fear of balloons, called globophobia, by training to win Guinness World Record titles for balloon inflation.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

Hotels in Cannes, the glamorous city on the French Riviera, hire hawks to ward off seagulls during the city's famous film festival.

Before the current East Wing ballroom project, only two White House renovations in the past 100 years cost more than $10M.

Salvador Dalí believed he was his own dead brother, who had died nine months before he was born