Laughing gas is the common name for nitrous oxide (N₂O), a colorless, slightly sweet-smelling gas used in medicine and dentistry as a sedative and pain reliever. It works by calming anxiety and dulling pain perception, typically taking effect within minutes of inhalation. The nickname comes from the giddy, euphoric feeling it produces, which sometimes triggers laughter.
How Nitrous Oxide Works in the Brain
Nitrous oxide affects the brain through two main pathways. First, it blocks a type of receptor responsible for transmitting pain and excitatory signals between nerve cells. This is what produces the pain-relieving effect. Second, it influences the brain’s natural calming system, which is why people feel relaxed and less anxious while breathing it in.
The combination of these two actions makes nitrous oxide both an analgesic (pain reducer) and an anxiolytic (anxiety reducer). At higher concentrations, it can serve as a general anesthetic, though in most dental and outpatient settings it’s used at lower levels where you stay conscious and responsive throughout.
What It Feels Like
Most people describe the experience as a warm, floating sensation. You may feel lightheaded, tingly in your hands and feet, and generally unconcerned about whatever procedure is happening. Some people laugh or feel giddy. Mild visual or auditory changes can occur, though full hallucinations are uncommon at standard doses. The gas doesn’t put you to sleep. You can still hear your dentist, respond to questions, and breathe on your own.
The effects kick in fast, usually within a few minutes of breathing through the nose mask. Recovery is equally quick. Once the mask is removed and you breathe normal air, the gas clears from your system rapidly. Most people feel back to normal within minutes, which is one of the biggest advantages over other forms of sedation. You can typically drive yourself home afterward.
Common Uses
Dental offices are the most familiar setting for laughing gas. It’s routinely offered for fillings, root canals, extractions, and other procedures where patients feel anxious. In a standard dental setup, the nitrous oxide is always mixed with oxygen. Guidelines from the American Academy of Pediatric Dentistry specify that the oxygen concentration should never drop below 30%, and the nitrous oxide concentration typically stays at or below 50%.
Beyond dentistry, nitrous oxide is used in emergency rooms and pediatric units for painful but brief procedures like setting a broken bone, stitching a wound, or inserting an IV in a child. It’s particularly valued in pediatrics because it’s noninvasive, doesn’t require a needle, and wears off quickly. A large French survey of nearly 36,000 uses (mostly in children) found that only 4.4% experienced any side effects, and serious adverse events were extremely rare.
Side Effects
The most common side effects are mild and short-lived. These include dizziness, drowsiness, nausea, headache, and tingling sensations. Some people experience brief episodes of nausea or vomiting, particularly if the concentration is on the higher end or the procedure runs long. Balance problems can occur in the minutes right after the gas is turned off, which is why patients are typically given pure oxygen for a few minutes before standing up.
More unusual reactions include mild hallucinations, euphoria that tips into agitation, or brief confusion. These tend to resolve within minutes of stopping inhalation.
Who Should Avoid It
Nitrous oxide is considered safe for most people, but certain conditions make it a poor choice. Because the gas expands inside enclosed body spaces (it’s about 30 times more soluble than nitrogen), it’s unsafe for anyone with a collapsed lung, a bowel obstruction, or who has recently had middle ear or certain eye surgeries. The expanding gas can increase pressure in those areas and cause serious complications.
It’s also not recommended during the first trimester of pregnancy, because it interferes with vitamin B12 and folate metabolism, both critical for early fetal development. People with severe heart disease, pulmonary hypertension, or severe psychiatric disorders are generally advised to use alternative sedation.
The Vitamin B12 Problem
This is the most important long-term risk to understand, especially for people who use nitrous oxide recreationally. The gas inactivates vitamin B12 by chemically altering it. Vitamin B12 is essential for producing myelin, the protective coating around nerves, and for synthesizing DNA. When B12 can’t do its job, the consequences can be serious: nerve damage, numbness and weakness in the limbs, difficulty walking, and in severe cases, degeneration of the spinal cord.
For a single dental visit, this effect is clinically insignificant in healthy people. The body recovers its B12 function without issue. The danger comes from repeated or prolonged exposure. Recreational users who inhale nitrous oxide frequently from pressurized canisters are at real risk of B12 deficiency and the neurological damage that follows. Reported complications include peripheral neuropathy, bone marrow suppression, and psychosis. People who already have low B12 levels (common in vegans, older adults, and those with certain digestive conditions) are especially vulnerable, even with shorter exposure.
A Brief Origin Story
Nitrous oxide was first identified by the chemist Joseph Priestley in 1772, but it was Humphry Davy who explored its mind-altering properties in the late 1790s. Davy documented its ability to reduce pain and produce euphoria, publishing his findings in 1800. The leap to surgical use came in 1844, when a dentist named Horace Wells realized the gas could eliminate pain during tooth extractions. That moment is often cited as the birth of modern anesthesia. More than 175 years later, nitrous oxide remains one of the most widely used sedatives in medicine, largely because of its rapid onset, fast recovery, and strong safety record at clinical doses.