Some organic - that is, carbon based - compounds can produce effects similar to alcohol or anaesthetics when their vapours are inhaled. A number are used as solvents in glues, paints, nail varnish removers, dry cleaning fluids and de-greasing compounds. Others are used as propellant gases in aerosols and fire extinguishers or as fuels such as petrol or cigarette lighter gas (butane). Most households, factories and offices use a range of solvents which can be sniffed.

These products give off vapours or gases at normal temperatures and can be inhaled through the mouth or nose to give an intoxicating effect. This is sometimes called 'glue sniffing', 'solvent abuse' or 'volatile substance abuse' (VSA). Solvents are sometimes directly inhaled but are also sometimes sniffed from inside a plastic or paper bag or put on a rag before sniffing.

The rise of ecstasy use has tended to relegate solvent use to the sidelines as far as the media is concerned and it may well be that sniffing solvents is less of a craze than it was a few years ago. However, between 70 and 100 young people are still dying from solvent sniffing every year; some of these fatalities will be first time sniffers.

UInhaled solvent vapours are absorbed through the lungs and rapidly reach the brain. Breathing and heart rate slow down and repeated or deeper inhalation leads to feelings similar to being drunk with loss of co-ordination and disorientation. In some cases users momentarily lose consciousness but will normally come round quickly with no lasting damage. Users report visual distortions and peculiarities similar to hallucinations. The effects are short lived and usually less than 45 minutes without a repeat dose. As the effects wear off users often feel tired and drowsy and may experience a hangover.

Accidental death or injury can happen especially if youngsters are sniffing in an unsafe environment such as a canal or river bank, on a roof or near a busy road or train line. Sniffing to the point of becoming unconscious also risks death through choking on vomit. If the method of use obstructs breathing (such as an sniffing with a plastic bag over the head) death from suffocation may result. Some solvents (such as an aerosols and cleaning fluids) sensitise the heart to the effects of exertion and can lead to heart failure, especially if the user is running around. Gases in aerosols and lighter fuel refills squirted directly into the mouth can freeze the airways and lead to death through suffocation.

Very long term heavy use of solvents can damage the brain, kidneys and liver but this is very rare and more likely in industrial work where people work everyday in environments where solvents are used. Tolerance can develop with regular use so more is needed to get the same effect. Whilst physical dependence is not a problem, psychological dependence on the effects of solvents occurs with a small minority of users. These youngsters may come to rely on solvents to deal with unhappiness and underlying personal, family or social problems. They often sniff alone rather than in a group with friends. Long term regular use may also lead to people becoming very tired, forgetful and not being able to concentrate. Weight loss, depression and interference with kidney and liver functions can occur but these tend to clear up once sniffing stops.