Nitrous oxide, commonly called laughing gas, reduces anxiety and dulls pain during dental procedures. You breathe it in through a small mask over your nose, feel its effects within about 30 seconds, and return to normal within 5 to 10 minutes after the gas is turned off. It’s one of the mildest forms of sedation available, and most people can drive themselves home afterward.
How It Works in Your Brain
Nitrous oxide changes the way nerve cells communicate. Your brain has receptors that amplify signals (excitatory) and receptors that quiet them down (inhibitory). Nitrous oxide blocks the excitatory receptors, specifically the ones that respond to glutamate, your brain’s main “go” signal. With those receptors partially blocked, your nervous system dials down its activity, which is why you feel calm, slightly detached, and less sensitive to pain.
This blocking action also triggers a chain reaction that increases the release of certain chemical messengers involved in mood and relaxation. The net result is a state where you’re still conscious and can respond to your dentist, but discomfort and anxiety fade into the background.
What It Feels Like
The experience varies from person to person, but most people notice a warm, tingling sensation that starts in their hands and feet and spreads through the body. Your limbs may feel heavy, and sounds in the room can seem muffled or distant. Many people describe a floating or light-headed feeling, sometimes accompanied by mild giddiness, which is where the “laughing gas” nickname comes from.
You stay awake the entire time. You can hear your dentist, answer questions, and follow instructions. Some people feel slightly euphoric, while others simply feel relaxed and a bit drowsy. At typical dental concentrations (usually 30 to 40 percent nitrous oxide mixed with oxygen), the sedation is light enough that you remain fully aware of your surroundings. If the concentration creeps above 50 percent, side effects like dizziness, excessive sleepiness, or disorientation become more likely, which is why dental offices keep it well below that threshold.
How It’s Given
Your dentist places a fitted nasal mask, sometimes called a nasal hood, over your nose. You breathe normally through your nose while the dentist adjusts the mix of nitrous oxide and oxygen. Delivery systems are designed so the oxygen concentration never drops below 30 percent, which is actually higher than the 21 percent oxygen in normal room air. A built-in fail-safe automatically shuts off the nitrous oxide if the oxygen supply is interrupted.
The dentist can adjust the concentration throughout your appointment. They might lower it during a straightforward filling and increase it during something more uncomfortable like an extraction or the injection of local anesthetic. This flexibility is one of the reasons nitrous oxide remains so widely used: the level of sedation can be fine-tuned in real time.
A scavenging system built into the mask pulls excess gas away at about 45 liters per minute and vents it outside the building. This protects the dental team from repeated low-level exposure over the course of their workday.
How Quickly It Starts and Stops
Nitrous oxide is one of the fastest-acting sedatives in dentistry. Effects peak within roughly 30 seconds of inhalation and persist as long as you keep breathing the gas. Once the dentist switches you to pure oxygen at the end of your visit, the nitrous oxide clears your lungs quickly. Most people feel completely normal again within 5 to 10 minutes. Because it leaves your system so fast, you’re generally cleared to drive yourself home, unlike with oral sedatives or IV sedation, which typically require someone else to take you.
Nitrous Oxide for Children
Nitrous oxide is a go-to option in pediatric dentistry because it’s non-invasive and easy to reverse. The American Academy of Pediatric Dentistry considers it a safe tool for managing anxiety in kids, though its success depends heavily on the child’s ability to breathe through their nose and accept the nasal hood. A child who is crying uncontrollably or breathing through their mouth won’t inhale enough of the gas for it to work.
Flow rates are adjusted for smaller lungs. Older children and adults typically receive 5 to 7 liters per minute, while three- to four-year-olds need only 3 to 5 liters per minute. The concentration stays below 50 percent, and sessions ideally last under 45 minutes, since longer exposure and higher concentrations are linked to more negative outcomes in studies. A child’s temperament is one of the best predictors of whether nitrous oxide sedation will go smoothly.
Possible Side Effects
The most common side effect is nausea. Surgical studies comparing nitrous oxide to plain air found that about 29 percent of patients who received nitrous oxide experienced nausea or vomiting, compared to roughly 9 percent in the air-only group. In a dental setting, where procedures are shorter and concentrations are lower, the risk is smaller, but it’s still the main complaint. Eating a heavy meal right before your appointment can make this worse, which is why many offices suggest a light meal beforehand.
Other possible effects include headache, dizziness, and feeling unusually tired afterward. These are typically mild and short-lived. Serious reactions are rare in the dental setting because the concentrations used are moderate and the exposure time is brief.
Who Should Avoid It
Nitrous oxide is safe for most people, but certain conditions make it a poor choice. It interferes with the body’s ability to use vitamin B12, which plays a role in nerve function and red blood cell production. In healthy people, this effect is too small to matter. But for anyone who is already B12 deficient or critically ill, it can cause real problems, including a form of anemia and nerve damage.
Other situations where nitrous oxide is typically avoided include:
- First trimester of pregnancy, because of its impact on B12 and folate metabolism, which are critical for early fetal development
- Conditions involving trapped air, such as a collapsed lung or bowel obstruction, because nitrous oxide moves into closed air spaces 30 times faster than nitrogen moves out, causing dangerous pressure buildup
- Severe heart or lung disease, since nitrous oxide can raise pressure in the pulmonary arteries
- Severe psychiatric disorders, because the gas can occasionally cause hallucinations or vivid dreaming
- A rare genetic condition called MTHFR deficiency, which affects how the body processes folate; repeated nitrous oxide exposure in these individuals has been linked to serious spinal cord damage
If you have poor lung function or a history of severe motion sickness or post-procedure nausea, your dentist may suggest an alternative approach to sedation. For everyone else, nitrous oxide remains one of the safest and most predictable tools available for making dental visits more comfortable.