Around 18 per cent will lose up to two days of their holiday due to illness. So why do we often get sick at a time when we should be feeling better than ever?
It's not because our immune system goes on holiday as well.
According to the World Health Organisation (WHO) travellers simply expose themselves to a wide variety of risk factors, from changes in climate to foreign microbes, all in a relatively short period of time.
Fortunately, many common travel illnesses can be managed or even avoided with some common sense and forward planning.
The most common travellers' disease worldwide is diarrhoea. Travellers' diarrhoea is caused by the consumption of contaminated food and water and is most common in developing countries.
The most important treatment is re-hydration with clean water. Adding an electrolyte replacement such as Gastrolyte is also beneficial in severe cases.
Respiratory tract infection is the second most common travellers' illness, affecting up to 20 per cent of travellers. You have a higher risk of respiratory illness during travel because you will more often be in close proximity to large groups on tours, at tourist sites and on public transport.
The Travellers Medical and Vaccination Centre recommends decongestants and antihistamines to help to relieve symptoms.
Sun burn is also a surprisingly common illness for travellers. Australian travellers should know better but often an unfamiliar climate can mask the sun's intensity.
Some medications may also affect a person's sensitivity to UV radiation. The number one rule is to cover up as much overseas as you ideally should at home.
If you get stung by an insect, drink plenty of water and apply a cold compress to affected areas.
Contrary to popular belief, communicable diseases are not easily spread through aircraft ventilation systems, according to the WHO.
Cabin air and ventilation rates are very carefully controlled and recirculated air is passed through filters which remove bacteria and viruses.
If you get sick shortly after returning home it's more likely that you developed it before you boarded the plane - or you sat very near someone who was ill and coughing.
RAC members save 15% on travel insurance so you can stress less before your holiday.