It’s selling itself as a 21st-century playground, a world capital of tourism offering beach resorts to challenge the Caribbean, Parisian art and Hong Kong-style shopping in an environment that’s “safer than Singapore”. But draconian antidrug laws are undermining Dubai’s carefully cultivated fun-loving image.

Travel there with a bottle of cough mixture and you could catch a cold. Last week, the emirate’s authorities quietly released Cat Le-Huy, a 31-year-old tourist who was held for six weeks in the central prison at Al-Wathba after customs officials found melatonin pills - used to beat jet lag - and a speck of dirt that the authorities declared was hashish in his luggage.

He was lucky. Last month, the Radio 1 DJ Raymond Bingham - aka Grooverider - was jailed for four years for possessing 2.16 grams of cannabis. Whether he will serve the entire sentence depends on the whim of Dubai’s judiciary: the American record producer Dallas Austin, sentenced to four years when ecstasy was found in his possession, and Londoner Keith Brown, who received the same term after 0.003 grams of cannabis (an amount smaller than a pinhead) was discovered lodged in the tread of his shoes, were recently freed in prison amnesties.

Five other Britons, along with 19 French nationals and an Italian tourist, have been imprisoned for weeks or months for the alleged possession of even microscopic amounts of narcotics, but it’s not just recreational drug users who are at risk.

“What many travellers may not realise is that they can be deemed to be in possession of such banned substances if they can be detected in their urine or bloodstream, or in tiny trace amounts on their person,” says Catherine Wolthuizen of Fair Trials International. “We even have reports of the imprisonment of a Swiss man for ‘possession’ of three poppy seeds on his clothing after he ate a bread roll at Heathrow.

“We have seen a steep increase in such cases over the past 18 months. Customs authorities are using highly sensitive new equipment to conduct extremely thorough searches on travellers, and if they find any amount – no matter how minute – it will be enough to attract a mandatory four-year prison sentence.”

On the list of substances that travellers can be jailed for possessing are dozens of compounds used in over-the-counter remedies. These include Benylin children’s coughs and colds formula, which contains dextromethorphan, and Tixylix children’s cough syrup. Other products on a blacklist of more than 300 substances include the popular antidiarrhoea treatment Lomotil, cough treatments Coldex and Robitussin, and antidepressants Valium and Prozac. Possession of any of these without a prescription or an explanatory letter from your GP could lead to arrest and imprisonment.

And despite the fact that more than 800,000 British tourists will visit Dubai this year, none of the tour operators contacted by The Sunday Times offers information about what medicines can be taken into the emirate. “We would not put detailed banned substances on the website as this would be too much information to digest,” Kuoni said. “We do, however, refer clients, both in the brochure and links on the website, to the Foreign Office’s website.”

In its entry on Dubai, the Foreign Office advises: “Some over-the-counter medicines, such as codeine, are illegal without a doctor’s prescription. In some cases, you will be allowed to take these medicines in, providing they are in their original packaging and, in addition to the prescription, you provide a note from your GP outlining what the medicine is required for.” The definitive list can be found only as a file buried deep in the pharmacists’ section of the United Arab Emirates ministry of health’s website, but is it reasonable to expect families to ask GPs for a letter to cover a bottle of Tixylix bought in Boots?

“Along with the international community, Dubai has a clear policy regarding drug trafficking, smuggling and possession, and this is one of the reasons the emirate has one of the lowest crime rates in the world,” says Ian Scott of Dubai’s department of tourism. “This, in turn, is one of the many reasons it is such an attractive holiday destination.”

But Tixylix? “The message is clear,” Scott says. “Don’t take illegal drugs, and if you’re on medication, bring a prescription to prove it. We have hundreds of thousands of tourists every year, and the number stopped with illegal substances is infinitesimal.”

If you are one of that number, you could end up behind bars for weeks, months or even the mandatory four years, so it’s probably best to leave the Tixylix at home.

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