Why do we always get sick on holidays? An infectious diseases expert explains

You've tied up loose ends at work and you're on annual leave at last, heading off on a highly anticipated holiday. But what happens next was not part of your plan: you get sick.

New research from Compare the Market has found 73 per cent of Australian holidaymakers have experienced illness or injury while on holiday.

Perhaps more concerning, one in four of the 1000 Aussies surveyed in September 2025 have experienced gastro while travelling, which can land you in hospital if you have a particularly nasty case.

Holidays should be a time of relaxation and joy - so why are so many of us getting sick?

According to University of NSW associate professor at the School of Population Health and infectious diseases social scientist, Holly Seale, being exposed to new experiences and conditions while travelling - especially to different countries - can make us sick.

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The illnesses are gastro, food poisoning, flu, sexually-transmitted infections and vector-borne illnesses (such as those carried by mosquitoes).

But getting sick can also come down - in part - to your behaviours, including whether you're washing your hands as much as you do back at home.

"Unfortunately, what we know of travellers is that they do tend to be more risky when they're abroad, and sometimes think that the same rules don't apply, and are happy to engage in behaviours they may not do while they're here in Australia or at home," Dr Seale told Explore.

She recommended talking to your doctor before you go overseas to find out which vaccinations you will need, such as measles.

She also recommended following tried-and-true precautions like not drinking the tap water in countries where it could be contaminated, using mosquito repellent, washing your hands regularly, and not eating food that has been sitting out in the heat.

But is there any truth to the feeling some of us experience, where getting sick is our body's response to being relaxed?

Dr Seale said there is no science behind this and thinks it is a coincidence.

Compare the Market's survey shows one in four people have experienced gastro, one in four have come down with either a cold or flu, and one in five have had food poisoning while on holidays.

Other Australians also reported insect bites, COVID-19 and heat stroke while away.

Generation X and Baby Boomers were most likely to experience gastro on vacation, both at 30 per cent, while millennials (38 per cent) have had food poisoning more than any other generation.

Some respondents reported serious injuries on holidays including third-degree burns (2 per cent), vehicle crash wounds (2 per cent) and broken bones (1 per cent).