Holidays can be bad for your health, according to research suggesting that those who seek sex in the sun should be screened for infectious diseases when they return.
More than 30 million UK residents - about half the population - travel abroad each year, said a paper in the British Medical Journal.
Karen Rogstad, a consultant in the department of genito-urinary medicine at the Royal Hallamshire hospital in Sheffield, has found an "alarming increase" in the number of sexually transmitted infections. Foreign travel appears to be responsible for a small but significant proportion, including 21% of syphilis cases in men.
Nine per cent of people with gonorrhoea reported having sex abroad in the previous three months. Bisexual or gay men mostly had sex in the US and Europe, while hetero-sexual men had sex in the Caribbean or Far East.
Women mainly reported new sexual encounters in the Caribbean, the paper said.
Many new cases of HIV infection in the UK were the result of encounters abroad - a quarter of the UK-born women infected between 2000 and 2002, and 69% of men, of whom probably 22% were infected in Thailand.
"The ultimate risk holiday is that of the sex tourist" the author said.
GPs should give warnings on sex risks when people went for health advice before travelling. "Men travelling alone to Thailand and the Philippines on holiday are likely to be sex tourists and require advice on condom use and provision of hepatitis B vaccination," she wrote. Travellers should be told that they could pick up infections from oral as well as vaginal and anal sex.
Young people should be encouraged to go for a sexual health check when they returned, and doctors should ask any patient consulting them with any symptoms that might suggest a sexually transmitted infection whether they - or their own sexual partner in the UK- had recently travelled abroad.
• Teenagers are no better than adults at getting the "safe sex" message over to under-16s, according to a study published today in the Lancet.
Researchers studied the sex education lessons of 8,000 pupils. Half were taught by adults and half by older pupils.
There was not a significantly lower incidence of unsafe sex before the age of 16 among the peer-taught group.
