Sometimes air comes out of your mouth. 

Sometimes air comes out of your mouth. 

A burp is when gas comes out of the mouth. 
You might swallow extra air if you chew gum or talk while eating. Babies often need help burping. You can hold a baby against your shoulder and pat their back. 
A burp, or belching, is the sound of gas escaping the upper digestive tract. This gas moves from the esophagus and stomach into the throat. Usually, the gas then exits through the mouth. 

Most burps happen because we swallow air while eating or drinking. This air cannot be absorbed by the body. To get rid of it, the air rises from the stomach. It moves up through the esophagus by passing a relaxed muscle. This muscle is called the lower esophageal sphincter. When the gas fills the esophagus, it triggers a belch reflex. This reflex makes the upper muscle relax and open. The gas then enters the throat and escapes. 
People can swallow more air by chewing gum or sucking on candy. Talking while eating or smoking can also increase burping. Some people swallow air as a nervous habit. Drinking bubbly drinks like beer can cause burps filled with carbon dioxide. For babies, burping is very important for comfort. Adults often hold a baby against their shoulder to help. They might pat the baby's back to release the gas. 
Different cultures have different rules about burping. In Japan, burping during a meal is seen as bad manners. In North America and Europe, it is often seen as impolite. However, some South Asian cultures view it differently. A guest might burp to show the host that the meal was satisfying. There are also records for burping. In 2021, Neville Sharp from Darwin, Australia, set a record. His burp was 112.4 decibels loud. That is about as loud as a jet engine. 
Many mammals like cows and sheep burp quite often. Ruminants, which are animals like cows, produce a lot of methane gas. This gas comes from tiny living things in their gut. A single lactating cow can produce 322 grams of methane every day. This can affect the environment and the greenhouse effect. Scientists in Perth, Australia, are looking for ways to help. They are studying red algae called Asparagopsis taxiformis to change cow diets. They are even working on a vaccine to reduce methane. 
Belching, also known as eructation or burping, is the audible release of gas from the upper gastrointestinal tract. This tract includes the esophagus and the stomach. The gas moves into the pharynx, which is the throat, and usually exits through the mouth. While it is a normal part of eating and drinking, excessive belching can indicate a medical problem. When belching becomes a chronic issue, it is classified as a belching disorder. These are considered disorders of gut-brain interaction, or DGBIs. 
The process of belching relies on a specific biological mechanism called the belch reflex. Most air swallowed during meals cannot be absorbed by the digestive system. To remove this air, it must rise from the stomach into the esophagus. This happens when the lower esophageal sphincter, a ring of muscle, relaxes. As the gas fills the esophagus, it creates gaseous distention, which is a stretching sensation. This stretching triggers the belch reflex. The reflex causes the upper esophageal sphincter to relax and open. The gas then enters the pharynx and is expelled. 
There are two distinct types of belching disorders. The first is supragastric belching, which occurs in the esophagus rather than the stomach. This type is considered voluntary and is often linked to anxiety. Because the reflux in these episodes is mainly non-acidic, medications like proton pump inhibitors are often ineffective. The second type is gastric belching, which comes from the stomach itself. This is an involuntary process. In this case, gas collects in the cardia, the area near the lower esophageal sphincter. This volume stimulates stretch receptors in the stomach wall. This triggers a vagovagal reflex, causing a transient lower esophageal sphincter relaxation, or TLESR.
While most people can belch easily, some face a condition called abelchia. This is an inability to belch known as retrograde cricopharyngeus dysfunction (R-CPD). It can also be called retrograde upper esophageal sphincter dysfunction (R-UESD). In this condition, the cricopharyngeus muscle fails to relax. R-CPD was first discovered in 1987, and research into the condition increased during the mid to late 2010s. Patients may experience stomach rumbling, bloating, and flatulence. They might also suffer from nausea, constipation, or even shortness of breath. Doctors can assess this using high-resolution manometry or fluoroscopy. Many patients find success with a single Botox injection, though a partial cricopharyngeal myotomy is another option.
Social views on belching vary significantly across the globe. In Japan, burping during a meal is viewed as bad manners. Similarly, Western cultures in North America and Europe generally consider it impolite. However, in some South Asian cultures, it is viewed differently. A guest might burp to signal to the host that the meal was satisfying and they are full. There are also extreme examples of belching, such as the Guinness World Record. In 2021, Neville Sharp from Darwin, Australia, set a record with a burp measuring 112.4 dB. This volume is approximately as loud as a jet engine.
Belching is also a major factor in environmental science regarding ruminant animals. Ruminants, such as cows and sheep, produce large amounts of methane gas during digestion. This methane is produced by a specific group of methanogenic archaea in the gut. Interestingly, bacteria like Escherichia coli do not produce methane because they lack the necessary enzymes. A single lactating cow can produce about 322g of methane per day. This totals more than 117 kg of methane per year through burping and exhalation. Because 95% of this gas is emitted through burping, commercially farmed cows contribute 37% of anthropogenic methane emissions. 
Scientists are working on several ways to mitigate these environmental effects. Researchers at the Commonwealth Scientific and Industrial Research Organisation in Perth, Australia, are developing an anti-methanogen vaccine. Another strategy involves modifying animal diets. For example, adding the red algae Asparagopsis taxiformis to feed can help. Some farmers have already seen success by switching from corn and soy to alfalfa and flaxseed. These foods are closer to the natural grasses that these animals ate before they were domesticated. Understanding these biological processes helps us manage both human health and global environmental impacts.
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