Inhalants are a broad range of drugs in the forms of gases, aerosols, or solvents that are breathed in and absorbed through the lungs. While some inhalant drugs are used for medical purposes, as in the case of nitrous oxide (a dental anaesthetic), this article focuses on the non-medical use of inhalants, as recreational drugs that are used for their intoxicating effect. Most inhalant drugs that are used non-medically are ingredients in household or industrial chemical products that are not intended to be concentrated and inhaled, including organic solvents (found in cleaning products, fast-drying glues, and nail polish removers), fuels (gasoline (petrol) and kerosene) and propellant gases such as freon and compressed hydrofluorocarbons that are used in aerosol cans such as hairspray, whipped cream and non-stick cooking spray. A small number of recreational inhalant drugs are pharmaceutical products that are used illicitly, such as anaesthetics (ether and nitrous oxide) and volatile anti-angina drugs (alkyl nitrites).
Inhalant users tend to be people who do not have access to other drugs or alcohol, such as children, teenagers, incarcerated or institutionalized people, and marginalized individuals. The most serious inhalant abuse occurs among children and teens who "...live on the streets completely without family ties." Inhalant users inhale vapor or aerosol propellant gases using plastic bags held over the mouth or by breathing from a solvent-soaked rag or an open container. The effects of inhalants range from an alcohol-like intoxication and intense euphoria to vivid hallucinations, depending on the substance and the dosage. Some inhalant users are injured due to the harmful effects of the solvents or gases, or due to other chemicals used in the products that they are inhaling. As with any recreational drug, users can be injured due to dangerous behavior while they are intoxicated, such as driving under the influence. In some cases, users have died from hypoxia (lack of oxygen), pneumonia, cardiac failure or arrest, or aspiration of vomit.
Inhalant users inhale vapors or aerosol propellant gases using plastic bags held over the mouth or by breathing from an open container of solvents, such as gasoline or paint thinner. Nitrous oxide gases from whipped cream aerosol cans and aerosol hairspray or non-stick frying spray are sprayed into plastic bags. When inhaling non-stick cooking spray or other aerosol products, some users may filter the aerosolized particles out with a rag. Some gases such as propane and butane gases are inhaled directly from the canister. Once these solvents or gases are inhaled, the extensive capillary surface of the lungs rapidly absorb the solvent or gas, and blood levels peak rapidly. The intoxication effects occur so quickly that the effects of inhalation can resemble the intensity of effects produced by intravenous injection of other psychoactive drugs.
The effects of solvent intoxication can vary widely depending on the dose and what type of solvent or gas is inhaled. A person who has inhaled a small amount of rubber cement or paint thinner vapour may be impaired in a manner resembling alcohol inebriation. A person who has inhaled a larger quantity of solvents or gases, or a stronger chemical, may experience stronger effects such as distortion in perceptions of time and space, hallucinations, and emotional disturbances.
In the short term, many users experience headache, nausea and vomiting, slurred speech, loss of motor coordination, and wheezing. A characteristic "glue sniffer's rash" around the nose and mouth is sometimes seen after prolonged use. An odor of paint or solvents on clothes, skin, and breath is sometimes a sign of inhalant abuse, and paint or solvent residues can sometimes emerge in sweat.
Inhalants are a large class of drugs and therefore exhibit a variety of mechanisms of action. The mechanisms of action of many non-medical inhalants have not been well elucidated. Anesthetic gases used for surgery, such as nitrous oxide or enflurane, are believed to induce anesthesia primarily by acting as NMDA receptor antagonists, open channel blockers that bind to the inside of the calcium channels on the outer surface of the neuron, and provide high levels of NMDA receptor blockade for a short period of time.
This makes inhaled anesthetic gases different to other NMDA antagonists such as ketamine, which bind to a regulatory site on the NMDA-sensitive calcium transporter complex and provide slightly lower levels of NMDA blockade, but for a longer and much more predictable duration. This makes a deeper level of anesthesia achievable more easily using anaesthetic gases, but can also make them more dangerous than other drugs used for this purpose.
Alcohol is known to act as a GABA agonist, and it is likely that other solvents also act here to produce additional depressant effects. The solvent diethyl ether, for instance, has seen historical episodes of both inhalation and drinking, and produces effects suggestive of both NMDA and GABA mediated activity. The particular mix of NMDA antagonist vs GABA agonist properties will vary between solvents depending on molecular size or shape, and so the effects of particular solvents will differ, although all tend to share a similar profile.
Some inhalant users are injured due to the harmful effects of other chemicals used in the industrial solvents or fuels that they are inhaling (e.g., tetra-ethyl lead used in some fuels ). As with many recreational drugs, users can also be injured due to dangerous behaviour while they are intoxicated. In some cases, inhalant users can be injured or killed due to the effects of inhaling solvents or gases, which can cause hypoxia (lack of oxygen), pneumonia, cardiac failure or arrest, or aspiration of vomit. The inhaling of some solvents can cause hearing loss, limb spasms, and damage to the central nervous system and brain. Serious but potentially reversible effects include liver and kidney damage and blood oxygen depletion. Death from inhalants is generally caused by a very high concentration of fumes. Deliberately inhaling solvents from an attached paper or plastic bag or in a closed area greatly increases the chances of suffocation. Brain damage is typically seen with chronic long term use as opposed to short term exposure.
Of more concern from a toxicological perspective, or from the point of view of an individual considering the recreational use of solvents, is the additional toxicity resulting from either the physical properties of the compound itself, or additional ingredients present in a product. Many solvents of abuse are fairly toxic compounds that often produce liver and brain damage after prolonged use. This is particularly detrimental with chlorinated compounds such as carbon tetrachloride or chloroform, or when products containing mixtures of many substances such as solvent-based glue or paint is inhaled. Toxicity may also result from the pharmacological properties of the drug; excess NMDA antagonism can completely block calcium influx into neurons and provoke cell death through apoptosis, although this is more likely to be a long term result of chronic solvent abuse than a consequence of short term use.
Precise statistics on deaths caused by inhalant abuse are difficult to determine, as it is considered a dramatically under-reported cause of death due to the common result of a cause-of-death determination being attributed to the side-effects of inhalant abuse, such as a blood vessel rupture in the brain or a heart attack, rather than to the abuse itself. Inhalant use or abuse was mentioned on 144 death certificates in Texas during the period 1988-1998 and was reported in 39 deaths in Virginia between 1987 and 1996 from acute voluntary exposure to abused inhalants.
Nitrous oxide does not cause brain or organ damage, but can cause vitamin B12 depletion.
Use of some inhalants can cause brain, nerve, liver and other damage to the body. In the short term, death from solvent abuse occurs most commonly from aspiration of vomit while unconscious, or from a combination of respiratory depression and hypoxia, the second cause being especially a risk with heavier than air vapors such as butane or gasoline vapor. Deaths typically occur from complications related to excessive sedation and vomiting. Actual overdose from the drug does occur, however, and indeed inhaled solvent abuse is statistically more likely to result in life-threatening respiratory depression than intravenous use of opiates such as heroin. Most deaths from solvent abuse could be prevented if individuals were resuscitated quickly when they stopped breathing and their airway cleared if they vomited. However, most inhalant abuse takes place when people inhale solvents by themselves or in groups of people who are intoxicated. Certain solvents are more hazardous than others, such as gasoline.
Hypoxia can occur when inhalant users are huffing from a plastic bag over their face, which means that they are not breathing enough oxygen. Also, since many solvents are highly flammable (e.g., gasoline, paint thinner), some users have suffered burn injuries and deaths due to fires. Female inhalant users who are pregnant may have adverse effects on the fetus and the baby may be smaller when it is born, and may need additional health care. There is some evidence of birth defects and disabilities in babies born to women who sniffed solvents such as gasoline. Driving while using solvents presents the same dangers as other types of impaired driving because many solvents cause an alcohol-type intoxication.
Inhaling butane gas can cause drowsiness, narcosis, asphyxia, cardiac arrhythmia and frostbite. Butane is the most commonly misused volatile solvent in the UK, and caused 52% of solvent related deaths in 2000. By spraying butane directly into the throat, the jet of fluid can cool rapidly to –20 °C by expansion, causing prolonged laryngospasm. Some inhalants can also indirectly cause sudden death by cardiac arrest, in a syndrome known as "sudden sniffing death" The anesthetic gases present in the inhalants appear to sensitize the user to adrenaline. In this state a sudden surge of adrenaline (e.g., from a frightening hallucination or run in with the law), can cause a fatal cardiac arrhythmia.
Nitrous oxide gas can cause death by asphyxiation if a user inhales directly from a large tank using a mask or tube. Normally with recreational use, users get oxygen because they continue to breathe after inhaling the nitrous oxide from a bag or balloon. In a medical or dental setting, nitrous oxide is normally administered in combination with oxygen. With recreational use, if a mask is attached directly to the tank, then the user gets pure nitrous oxide with no way to take in any oxygen. The rapidly-expanding gas causes very cold temperatures that can freeze the lips and throat if the gas is inhaled directly from a tank or "whippit" aerosol container. Releasing the gas into a balloon first allows the gas to expand and warm before it is inhaled.
Inhalant drugs are often used by children, teenagers, incarcerated or institutionalized people, and impoverished people, because these solvents and gases are ingredients in hundreds of legally-available, inexpensive products, such as deodorant sprays, hair spray, and aerosol air fresheners. However, most users tend to be "...adolescents (between the ages of 12 and 17)" In some countries, chronic, heavy inhalant use is concentrated in marginalized, impoverished communities. Young people who become chronic, heavy inhalant abusers are also more likely to be those who are isolated from their families and community. The article Epidemiology of Inhalant Abuse: An International Perspective notes that "[t]he most serious form of obsession with inhalant use probably occurs in countries other than the United States where young children live on the streets completely without family ties. These groups almost always use inhalants at very high levels (Leal et al. 1978). This isolation can make it harder to keep in touch with the sniffer and encourage him or her to stop sniffing."
The article also states that "...high [inhalant use] rates among barrio Hispanics almost undoubtedly are related to the poverty, lack of opportunity, and social dysfunction that occur in barrios", and states that the "...same general tendency appears for Native-American youth", because "...Indian reservations are among the most disadvantaged environments in the United States; there are high rates of unemployment, little opportunity, and high rates of alcoholism and other health problems." There are a wide range of social problems associated with inhalant use such as feelings of distress, anxiety and grief for the community; violence and damage to property, violent crime, stresses on the juvenile justice system, and stresses on youth agencies and support services.
Solvent abuse in developing countries attacks youths in their most productive years. The ease of access of solvents and aerosols in developing countries could have economic ties as it may be related to the introduction of Structural Adjustment Programs (SAP) in the country. Since SAP’s may cause poverty, as well as education suffering financial support, this could explain why the youth’s in countries such as those in Latin America have an ease of access to and abuse solvents. 
Glue and gasoline sniffing is also a problem in parts of Africa, especially with street children and South Asia, three of the most widely abused inhalants are the Dendrite brand and other forms of contact adhesives and rubber cements manufactured in Kolkata, toluenes in paint thinners and Iodex - a muscle stress relieving balm. Another very common inhalant is Erase-X, a correction fluid that contains toluene. It has become very common for school and college students to use it because it is easily available in stationery shops in India. This fluid is also used by street and working children in Delhi. In some African countries, an inhalant known as Jenkem, derived from fermented human feces, is reportedly used by homeless orphans. In 2007 a media-driven panic arose regarding use of Jenkem by schoolchildren in North America, but appears to have been unfounded and based on an Internet hoax.
In the UK, marginalized youth use a number of inhalants, such as solvents and propellants. As well, in the UK rave culture, inhalants such as nitrous oxide "whippets" and amyl nitrite poppers are used to enhance the effect of the electronic dance music. In Russia and Eastern Europe, gasoline sniffing became common on Russian ships following attempts to limit the supply of alcohol to ship crews in the 1980s. The documentary Children Underground depicts the huffing of a solvent called Aurolac (a product used in chroming) by Romanian homeless children.
In Canada, native children in the isolated Northern Labrador community of Davis Inlet were the focus of national concern in 1993 when many were found to be sniffing gasoline. The federal Canadian and provincial Newfoundland and Labrador governments intervened on a number of occasions, sending many children away for treatment. Despite being moved to the new community of Natuashish in 2002, serious inhalant abuse problems have continued. Similar problems were also reported in Sheshatshiu in 2000. In Mexico, the inhaling of a mixture of gasoline and/or industrial solvents, known locally as "Activo" or "Chemo", has risen in popularity among the homeless and among the street children of Mexico City in recent years. The mixture is poured onto a handkerchief and inhaled while held in one's fist.
In the US, Ether was used as a recreational drug during the 1930s Prohibition era, when alcohol was made illegal. Ether was either sniffed or drunk, and in some towns replaced alcohol entirely. However, the risk of death from excessive sedation or overdose is greater than that with alcohol, and ether drinking is associated with damage to the stomach and gastrointestinal tract. Use of glue, paint and gasoline became more common after the 1950s. Abuse of aerosol sprays became more common in the 1980s as older propellants such as CFCs were phased out and replaced by more environmentally friendly compounds such as propane and butane. Most inhalant solvents and gases are not regulated under illegal drug laws such as the United States' Controlled Substances Act. However, many US states and Canadian cities have placed restrictions on the sale of some solvent-containing products to minors, particularly for products widely associated with "sniffing", such as model cement. The practice of inhaling such substances is sometimes colloquially referred to as huffing, sniffing (or "glue-sniffing"), dusting, or chroming.
Australia has long faced a petrol (gasoline) sniffing problem, especially in isolated and impoverished aboriginal communities. Although some sources argue that sniffing was introduced by United States servicemen stationed in the nation's Top End during World War II, or through experimentation by 1940s-era Cobourg Peninsula sawmill workers, other sources claim that inhalant abuse (such as glue inhalation) emerged in Australia in the late 1960s. Chronic, heavy petrol sniffing appears mainly to occur among remote, impoverished indigenous communities, where the ready accessibility of petrol has helped to make it a common substance for abuse.
In Australia, petrol sniffing now occurs widely throughout remote aboriginal communities in the Northern Territory, Western Australia, northern parts of South Australia and Queensland. The number of people sniffing petrol goes up and down over time as young people experiment or sniff occasionally. 'Boss' or chronic sniffers may move in and out of communities; they are often responsible for encouraging young people to take it up.
A 1983 survey of 4,165 secondary students in New Lydiate showed that solvents and aerosols ranked just after analgesics (e.g., codeine pills) and alcohol for drugs that were abused. This 1983 study did not find any common usage patterns or social class factors. The causes of death for inhalant users in Australia included pneumonia, cardiac failure/arrest, aspiration of vomit, and burns. In 1985, there were 14 communities in Central Australia reporting young people sniffing. In July 1997, it was estimated that there were around 200 young people sniffing petrol across 10 communities in Central Australia. Approximately 40 were classified as 'chronic' sniffers. There have been reports of young Aboriginal people sniffing petrol in the urban areas around Darwin and Alice Springs.
In 2005, the Government of Australia and BP Australia began the usage of Opal fuel in remote areas prone to petrol sniffing. Opal is a non-sniffable fuel (which is much less likely to cause a "high"), and has made a difference in some indigenous communities.
Inhalant use, especially glue sniffing, is widely associated with the late 1970s punk youth subculture in the UK and North America. Raymond Cochrane and Douglas Carroll claim that when glue sniffing became widespread in the late 1970s, it was "...adopted by punks because public [negative] perceptions of sniffing fitted in with their self-image" as rebels against societal values. While punks at first used inhalants "...experimentally and as a cheap high, adult disgust and hostility [to the practice] encouraged punks to use glue sniffing as a way of shocking society". As well, using inhalants was a way of expressing their anti-corporatist DIY (Do It Yourself) credo ; by using inexpensive household products as inhalants, punks did not have to purchase industrially-manufactured liquor or beer. One history of the punk subculture argues that "substance abuse was often referred to in the music and did become synonymous with the genre, glue sniffing especially" because the youths' "...faith in the future had died and that the youth just didn’t care anymore", due to the "awareness of the threat of nuclear war and a pervasive sense of doom". In a BBC interview with a person who was a punk in the late 1970s, they said that "there was a real fear of imminent nuclear war - people were sniffing glue knowing that it could kill them, but they didn't care because they believed that very soon everybody would be dead anyway."
A number of 1970s punk rock and 1980s hardcore punk songs refer to inhalant use. The Ramones, an influential early US punk band, referred to inhalant use in several of their songs. The song "Now I Want to Sniff Some Glue" describes adolescent ennui and the song "Carbona not Glue" states that "My brain is stuck from shooting glue". An influential punk fanzine about the subculture and music took its name ("Sniffin' Glue") from the Ramones song. The 1980s punk band The Dead Milkmen wrote a song, "Life is Shit" from their album "Beelzebubba" about two friends hallucinating after sniffing glue. Punk band-turned hip hop group, the Beastie Boys, penned a song "Hold it Now - Hit It," which includes the line "cause I'm beer drinkin, breath stinkin, sniffing glue." Pop punk band Sum 41 wrote a song "Fat Lip," which refers to a character who does not "... make sense from all the gas you be huffing..."
Inhalants are also referred to by bands from other genres, including several grunge bands—an early 1990s genre that was influenced by punk rock. The 1990s grunge band Nirvana, which was influenced by punk music, penned a song "Dumb", in which Kurt Cobain sings "my heart is broke/But I have some glue/ help me inhale /And mend it with you". L7, an all-female grunge band, penned a song entitled "Scrap" about a skinhead who inhales spray paint fumes until his mind "starts to gel". The Beck song "Fume" from his "Fresh Meat and Old Slabs" release is about inhaling nitrous oxide. Another Beck song, "Cold Ass Fashion," contains the line, "O.G. - Original Gluesniffer!" The band Primus's 1998 song "Lacquer Head" is about adolescents who use inhalants to get high. Hip hop performer Eminem wrote a song, "Bad Meets Evil," which refers to breathing "...ether in three lethal amounts." "The Brian Jonestown Massacre" a retro-rock band from the 1990s has a song entitled "Hyperventilation," which is about sniffing model airplane cement.
A number of films have depicted or referred to the use of solvent inhalants. In the 1980 comedy film Airplane!, the character of McCroskey (Lloyd Bridges) refers to his inhalant use when he states that "I picked the wrong week to quit sniffing glue." In the 1996 film Citizen Ruth, the character Ruth, a homeless drifter, is depicted inhaling patio sealant from a paper bag in an alleyway. In the comedy Love Liza, the main character, played by Philip Seymour Hoffman, develops an addiction to inhaling gasoline vapor of remote-controlled airplanes in the wake of his wife's suicide. Harmony Korine's 1997 film Gummo depicts adolescent boys inhaling contact cement for a "high". Edet Belzberg's 2001 documentary Children Underground chronicles the lives of Romanian street children addicted to inhaling paint. Yet another film that depicts the drug use is The Basketball Diaries in which a group of boys are huffing "carbona cleaning liquid" at 3 minutes and 27 seconds into the movie and farther into the movie a boy is reading a diary describing the experience of sniffing the cleaning liquid.
Films have also depicted the use of gas-based or aerosol inhalants. In the David Lynch film Blue Velvet, the bizarre and manipulative character played by Dennis Hopper uses a mask to inhale an unknown gas. In Little Shop of Horrors, Steve Martin's character dies from nitrous oxide inhalation. The 1999 independent film Boys Don't Cry depicts two young low-income women inhaling aerosol computer cleaner (Canned Air) for a "buzz." In The Cider House Rules, Michael Caine's character is addicted to inhaling ether vapours. The independent dramedy "Love Liza", Philip Seymour Hoffman plays a man who takes up building remote-controlled airplanes as a hobby to give him an excuse to huff the fuel in the wake of his wife's suicide. Thirteen, the main character, a teen, uses a can of aerosol computer cleaner to get high. In the action movie Shooter, an ex-serviceman on the run from the law (Mark Wahlberg) inhales nitrous oxide gas from a number of Whip-It! whipped cream canisters until he becomes unconscious. The film Fear and Loathing in Las Vegas describes how the two main characters inhale diethyl ether and amyl nitrite. The South African film The Wooden Camera also depicts the use of inhalants by one of the main characters, a homeless teen. The Wood Camera depicts the use of the inhalant in terms of socio-economic stratification. The titular characters in Samson and Delilah sniff petrol; in Samson's case, possibly causing brain damage.