Four people have died and six British backpackers are in hospital in South East Asia after reports of suspected methanol poisoning.

Simone White, 28, from Orpington in Kent, is among those who fell ill after being offered “free shots” in the Laos resort of Vang Vieng.

Bianca Jones, 19, from Melbourne, Australia, two Danish women in their 20s and a 56-year-old US citizen reported to have died.

New Zealand has confirmed that one of its citizens has also fallen ill.

Authorities are now warning travelers about the risks of methanol poisoning, how it happens and how to avoid it.

What is methanol?

Methanol, or CH3OH, is very similar to ethanol – the pure form of alcohol in alcoholic beverages.

Although it is an odorless, tasteless and highly flammable liquid like ethanol, it has a different chemical structure that makes it poisonous to humans.

Methanol, also known as wood alcohol, is commonly used to make solvents, pesticides, paint thinners and alternative fuels.

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What makes it so dangerous is the way our body metabolizes it.

Once consumed, our enzymes metabolize methanol into formaldehyde, the substance used to make industrial glues and embalming agents, before breaking down into formic acid.

“The formic acid disrupts the acid balance in the blood and the main consequence is primarily the effect on a person’s breathing. There are effects on many other organs including the kidney,” says Professor Alastair Hay, Emeritus Professor of Environmental Toxicology at the University of Leeds. .

“Formaldehyde attacks the nerves, especially the optic nerve, and blindness is a potential risk,” he adds.

How does it end up in alcoholic drinks?

In Southeast Asia and other popular tourist destinations, methanol can be found in alcoholic beverages for two main reasons.

First, it is cheaper than ethanol, so it is sometimes added to cut costs before the counterfeit alcohol is bottled and sold in stores and bars.

It can also happen accidentally if alcohol is homemade, which is common throughout Southeast Asia.

When alcohol is distilled and fermented without appropriate monitoring, methanol can sometimes be formed in toxic amounts.

Because it is impossible to tell the difference between methanol and ethanol content without specialist equipment, homemade drinks are often offered to tourists without anyone knowing how dangerous they are.

What are the symptoms of methanol poisoning?

Methanol is highly toxic, so just 25 ml can be fatal.

Methanol poisoning can be treated by using ethanol to counteract its effects on the body, but only within the first 10 to 30 hours after consumption.

This makes early diagnosis and warnings to others crucial.

The most common symptoms are:

• Vomiting and nausea;
• Vision changes, including blurriness, vision loss, and difficulty seeing bright light;
• Abdominal and muscle pain;
• Dizziness and confusion;
• Drowsiness and fatigue.

The symptoms of methanol poisoning are similar to those of alcohol poisoning, but are often more severe. If drinks are left unattended or your symptoms are disproportionate to the amount you drank, methanol poisoning may be occurring, authorities warn.

How is it treated?

Professor Hay says the treatment involves removing methanol from the blood via dialysis – while ‘keeping someone slightly drunk’ by giving them ethanol at the same time.

“The principle behind administering ethanol is quite simple; it slows methanol metabolism,” he says.

“Both alcohols are broken down by the same liver enzyme alcohol dehydrogenase. But the enzyme prefers ethanol.

“Ethanol thus acts as a competitive inhibitor that largely prevents the breakdown of methanol, but slows it down considerably, allowing the body to remove methanol from the lungs and some through the kidneys, and some through sweat.”

This avoids the process by which methanol is ultimately converted into formic acid, he adds.

How can you avoid this while traveling?

The UK travel advice for Laos and other parts of the region advises that the drinks most affected are:

• Local spirits, such as rice and palm liquor, are often labeled as ‘special’ or ‘happy’ drinks;
• Mixed drinks based on spirits, such as cocktails;
• Counterfeit branded bottled alcohol sold in bars and shops.

To minimize risks, travelers should:

• Only buy alcohol from licensed bars, hotels or shops;
• Check the labels on plate bottles may be counterfeit, including poor print quality or spelling errors;
• Avoid homemade alcohol;
• Check that bottles are properly closed before drinking from them;
• Avoid free drinks that you have not seen served yourself;
• Do not leave drinks and food unattended.