A healthy glow, a chilled out attitude and maybe even a sombrero - all perfectly fine to bring back from abroad. But watch out for those gruesome gut stowaways, says Peta Bee

Any products in this article have been selected editorially however if you buy something we mention, we may earn commission

There are many things you might want to bring back from your holiday - an outer glow, an inner sense of calm. Less appealing is the prospect of returning with a souvenir that is likely to leave you drained and exhausted, with stabbing stomach cramps and a growing sense of anxiety about what is behind it all. If you are eating right now, I urge you to stop before reading on. For the cause of such post-vacation trauma might be the stuff of nightmares: a gut infected with intestinal parasites, that take any opportunity to inhabit the human body.

Cases of parasitic infection are widespread, caused by eating contaminated food, poor hygiene habits and swimming in infested waters. Hookworm, among the most common holiday-bourne parasites, is contracted through exposure to faeces and infected soil. Celebrities are not immune from the gruesome insiders. In her cook book, It’s All Good , Gwyneth Paltrow tells of the time she fainted at a family lunch and later found she had a blood parasite and digestive problems. Her doctor, Alejandro Junger, prescribed an elimination diet to kill off the blighters and restore her health. And in 2011, when he swam the 140-mile length of the Thames to raise money for Sport Relief, David Walliams described how he contracted giardiasis - a disease caused by the tiny parasite giardia lamblia which he picked up in the Thames water and which gave him an upset stomach. He’s not alone. More than 50,000 people in Britain are thought to be infected by that parasite alone every year.

You are not immune at home

Dr Tim Woodman, medical director at Bupa, says a variety of intestinal parasites are common in the UK, mostly spread by poor handwashing habits or infected food (such as undercooked pork and beef). Roundworms, whipworms and flukes are the most common, often caught through eating vegetable and salad crops with parasite eggs on them or drinking infected water. Symptoms range from none at all to mild abdominal pain, itching and diarrhoea. Many people are unaware they have an infection until they spot a worm in their faeces. “Typically, if you contract a parasite in the UK it’ll cause irritation around your back-passage,” Dr Woodman says. “Some worms, such as tapeworms will simply break off.”

Potentially more serious, though, are parasites caught on holiday. “If you’ve contracted something overseas, it can cause more severe abdominal pain, anaemia (through making the bowel bleed) or even sudden weight loss (by absorbing nutrients from your food),” Dr Woodman says. “In these cases you’ll be advised on the correct medication to take.”

How are they treated?

Conventional treatment of parasitic conditions such as giardiasis is with antibiotics and there are several treatments available for roundworm and other parasites commonly contracted in the UK. Walliams made a full recovery. But left undiagnosed the condition can lead to gut problems mistaken for irritable bowel syndrome and symptoms of chronic fatigue.

The internet is awash with anecdotal evidence for various alternative remedies, including internal cleanses that claim to eradicate parasites. Among the most popular remedy is pumpkin seeds, said to contain ‘tetracyclic triterpenes’ substances that are released upon chewing or grinding them up and which are toxic to gut worms.  Drinking a lot of water to help flush out your system might also help, although Dr Woodman stresses there is no convincing medical evidence for any of these approaches. The popularity of the pumpkin seed cleanse arose after a 2013 trial on 48 ostriches showed it to be beneficial for infected birds. If you suspect you have a parasite, it is important to see your doctor, he says. “I’d advise the whole household is treated as it can spread easily without people necessarily knowing they have been infected,” Woodman explains. “It’s best to be on the safe side and to avoid infecting everybody else.”

What to eat to keep parasites at bay

Experts at the University of Maryland medical centre recommend consuming more raw garlic, pomegranates, beetroot and carrots - all widely used in natural medicine to kill parasites. They cite a small study in which a mixture of honey and papaya seeds cleared stools of parasites in 23 out of 30 subjects. There’s anecdotal evidence that enzymes such as papain, found in the papaya plant and also available as a supplement , might help kill worms when taken before and after a meal and probiotics  are helpful for restoring a healthy gut microbiota following treatment.

They're not all bad

For centuries, parasitic infection was part and parcel of human life, but parasites have been largely eradicated thanks to our increasingly sterile lives. Some scientists now think re-introducing them can help to redress the balance, enabling the immune system to be prepared for anything harmful. A decade ago, I remember being startled - not to mention slightly queasy - when I interviewed Dr Alan Brown, a biochemist then based at the University of Nottingham (he is now at Cambridge), who made a chance discovery that caused him to question conventional wisdom about intestinal parasites. A long-time sufferer of hayfever, Dr Brown had tried every conceivable treatment to no avail. Then, on a field trip to New Guinea, he contracted hookworms – and his hayfever disappeared. Back home he began a self-experiment, monitoring the larvae eggs in his faeces and cross-referencing the results with the severity of his sniffing, sneezing and sore eyes. Hookworm, it seemed, had cured his problem. Since then, other researchers have tried ‘re-parasiting’ people - with impressive results, especially with inflammatory bowel disease. Last year, Professor Alex Loukas, a researcher at the Australian Institute for Tropical Health and Medicine at James Cook University, published a study suggested that infecting humans with hookworm cures coeliac disease, the autoimmune condition that causes severe reaction to gluten in food. Admittedly, the trial was small, but it provided a platform for potential treatments. Not that you should assume parasites are doing you good. Trials are performed under laboratory conditions and ignoring a suspected infection is certainly not advised. “If you’ve contracted something, you need to get it treated,” Woodman says.

Follow Peta on  Twitter . For more A Healthy Curiosity articles as well as wellbeing and beauty news,  sign up  to our newsletter.