It's a common ingredient used in industrial and household products like paint thinners, antifreeze, varnish and even photocopier fluid. 

But now, methanol is attracting fresh attention over its role in the deaths of six foreign tourists who had drunk shots allegedly laced with the substance while on holiday in Laos — including that of a young British lawyer.  

Here, we reveal how the toxin can wreak havoc on the body within just hours of taking it, leaving drinkers paralysed, unable to breathe and at risk of losing their sight. 

Methanol, like the alcohol we consume in beer, wine and spirits, is a colourless liquid that smells similar to booze but is far cheaper to produce. 

But its effects are far more catastrophic. 

As little as half a shot, or 15ml, of a methanol-laced spirit can be enough to kill, experts say. 

Alarmingly, the noxious liquid is increasingly being used as a cheap alcohol substitute by unscrupulous shops and bars in certain holiday resorts — either replacing or being mixed with normal alcohol found in popular drinks. 

Symptoms of ingesting methanol can also vary depending on the person and how much is consumed. 

Typically, its effects take between just 40 minutes and 72 hours to appear, meaning rapid treatment of suspected methanol ingestion is vital. 

Early signs can mirror alcohol poisoning, with drinkers typically experiencing issues with co-ordination, balance and speech as well as confusion and vomiting. 

At the same time, blood pressure drops resulting in a woozy and faint feeling.   

Its numbing effect also makes users unresponsive more quickly. 

When in this state, drinkers may be uanable to coordinate their own muscle movement. 

Dr Wayne Carter, an associate professor at the University of Nottingham, said: 'Similar to alcohol it is oxidised in the body, but the breakdown of methanol forms a strong and dangerous acid — formic acid'.

This causes a person's blood to become acidic.

He added: 'It also forms a toxic product, formaldehyde, a cancer-causing chemical.'

In a marked difference to alcohol poisoning, if enough of this builds up, it can start to attack the nervous system — especially the optic nerve, which transmits messages between the brain and the eye.

According to the UK Health Security Agency, changes to vision often occur between 12 to 48 hours after ingesting methanol. 

Professor Sir Colin Berry, an expert in pathology at Queen Mary University of London, said these can range from mild sensitivity to light and 'misty or blurred vision' to 'visual hallucinations' such as dancing spots and flashes, or even 'partial or total loss of vision'. 

In later stages — around 18 to 48 hours after ingestion — the formic acid, which stops energy production in cells, causes the pH of the blood to drop, damaging tissues and organs in the body. 

This can lead to kidney failure, seizures and even gastrointestinal bleeding. 

'Drowsiness may progress to a coma', Sir Colin added.

A dramatic change in heart rate — speeding up rapidly or slowing down sharply — is often a sign of a 'fatal case', the Centers for Disease Control and Prevention (CDC) say. 

Its effect on muscle relaxation also suppresses the respiratory system, leading to sudden difficulty swallowing and making it harder for people to breathe. 

'Low blood pressure — hypotension — and respiratory arrest occur when death is imminent,' the CDC adds. 

Treatment often depends on the severity of the poisoning, but only blood tests can confirm this. 

Typically it involves removing methanol from the blood via dialysis, while 'keeping someone mildly drunk' by giving them alcohol at the same time, Professor Alistair Hay, an expert in toxicology at the University of Leeds, said. 

'The principle behind administering alcohol is quite simple — it delays methanol metabolism,' he added.

'Both are broken down by the same liver enzyme alcohol dehydrogenase. But the enzyme prefers alcohol.

'So it acts as an inhibitor by largely preventing methanol breakdown.

'It slows it down, allowing the body to vent methanol from the lungs and some through the kidneys, and a little through sweat.'

This avoids the process of methanol ultimately metabolising as formic acid, he added.

Warnings over the risks posed by the toxin come after the six deaths in Laos. 

The family of Australian teen Holly Bowles today confirmed the 19-year-old had died, more than a week after she fell ill in the tourist town of Vang Vieng.

Her friend Bianca Jones, 19 and British lawyer Simone White, 28, also died in the horrific incident alongside two Danish women, aged 19 and 20 and a 56-year-old American man. 

At least 11 other people are thought to remain in hospital. 

Ms White, Ms Jones and Ms Bowles were all staying at Nana Backpackers Hostel, where they were given free shots of liquor now thought to be laced with methanol.

Now the manager of the hostel, Duong Duc Toan, has reportedly been detained by local police, who said a 'number of' people had been taken into custody, but no charges have yet been filed. 

Staff previously vehemently denied shots given at their bar were responsible for the mass poisoning. 

But Ms White's friend, Bethany Clarke, a healthcare worker also from Orpington, took to the Laos Backpacking Facebook group to warn other travellers.

She said: 'Urgent — please avoid all local spirits. Our group stayed in Vang Vieng and we drank free shots offered by one of the bars. 

'Just avoid them as so not worth it. Six of us who drank from the same place are in hospital currently with methanol poisoning.'

The Foreign Office has issued guidance to Britons travelling to the country, warning them against consuming replica alcohol brands that may contain hidden amounts of methanol.

It says travellers are warned against consuming replica alcohol brands that may contain hidden amounts of methanol.

The latest advice states: 'Both male and female tourists have reported having their drink or food spiked with drugs and in some cases been assaulted. Never leave food or drink unattended.

'Be cautious about accepting drinks from strangers at bars, clubs, restaurants and parties.'

The recent wave of deaths and critical injuries comes a year after a coroner warned the British Government wasn't doing enough to warn travellers of the risk posed by contaminated alcoholic drinks following the death of a British woman in Indonesia. 

According to latest NHS data there were 15 A&E admissions of methanol poisoning in UK in 2023/24.

Many of these, however, are likely to be cases where products containing methanol for industrial purposes like windshield washer fluid or car antifreeze were accidentally consumed.