Officials have added travel alerts to eight new countries in a warning for travellers over methanol poisoning.
Methanol is a chemical cousin of ethanol, the kind of alcohol which you find in beer, wine, and spirits.
While ethanol is still not good for you at all, even if drank only in small quantities, methanol has far more acute symptoms.
These can include blindness and even death if someone drinks a large enough amount and doesn't get to hospital quickly.
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Unlicensed or street stalls selling alcohol are particularly high risk, as well as 'discounted' spirits or bucket cocktails, which can be popular in some tourist destinations.
Tourists visiting certain countries should be mindful if they are drinking, with the UK Foreign Office expanding its urgent guidance to several further countries.
The eight new nations added to the list are: Ecuador, Japan, Kenya, Mexico, Nigeria, Peru, Russia, and Uganda.
These join countries already on the list: Thailand, Laos, Vietnam, Cambodia, Indonesia, Turkey, Costa Rica, and Fiji.
Several tourists have ended up in serious condition after inadvertently drinking methanol on a night out.
One is Calum Macdonald, who was poisoned with methanol while on a trip to Laos.
Calum recalled his ordeal, telling the BBC: "I remember having this sort of kaleidoscopic, blinding light in my eyes and to the point at which I couldn't see anything."
Later, Calum's vision would be affected, with him recalling: "We were sitting in the hotel room, my friends and I, and I said to them: 'Why are we sitting in the dark? Someone should turn a light on.'"
Another person who ended up on the receiving end of methanol poisoning was Radharani Domingos, who had been visiting Brazil with friends and ended up being hospitalised for 15 days.
Speaking to Fantástico via G1, she said: "For a few moments I thought I was going to see my walls but I'm just groping.
"The revolt at this moment is to try to understand why they are tampering with the drink.
"They poisoned me and they are poisoning other people. It's disgusting that you order caipirinha and take methanol."
Others have not survived their ordeal, such as Simone White, 28, from Orpington, Kent, who died after drinking shots at a bar in Vang Vieng in Laos.
Strangely, treatment for methanol poisoning can involve binge drinking alcohol.
This is because methanol becomes dangerous in the body when it is metabolised, and consuming ethanol prevents the body metabolising it as it's instead processing the ethanol.
Unfortunately, as methanol becomes dangerous only as the body begins to process it, it can mean that symptoms may not present immediately after it is consumed.
Symptoms of methanol poisoning
The Foreign Office warns: "Spotting methanol poisoning can be difficult because at first it can affect you in the same ways as ‘real’ alcohol."
Signs to watch for include:
- Early signs: vomiting, poor judgement, loss of balance and drowsiness.
- 12-48 hours after drinking: abdominal pain, vertigo, hyperventilation, breathlessness, blurred vision and/or blindness, coma and convulsions. If you or someone you are travelling with have any of these symptoms seek urgent medical attention.
- Vision issues are a red flag and can also appear 12-48 hours after the first drink. Methanol poisoning can cause blurry vision, trouble looking at bright lights, and in some cases complete blindness. If you have “snowfield vision” (seeing snowy static like an old TV) or tunnel vision seek urgent medical help.
"Urgent medical attention could save your life or prevent serious complications," the Foreign Office added.
To prevent methanol poisoning you should avoid drinking spirits in bars where you think there's a risk, especially clear spirits.
Instead sealed bottles of beer are a better bet, or drinking in a licensed bar and only drinking known brands of spirits.
Most importantly, if you're not sure about a drink, don't drink it.
Kit Roberts