In short: The environment at your destination shapes your health risks abroad. Climate, altitude, insects, sanitation, the sun, the type of accommodation and even how you travel all affect which illnesses you might be exposed to. A pre-travel risk assessment looks at these factors so that advice on vaccines, malaria prevention and practical precautions fits your trip.

This guide, written by a Ready Health prescribing pharmacist, explains the main environmental health risks for travellers and how to reduce them.

Why does my destination change my health risks?

Many infections occur only in certain parts of the world, and some are seasonal. Malaria, dengue, yellow fever and Japanese encephalitis, for example, depend on the presence of particular mosquitoes. Risk can also differ between cities and rural areas within the same country, which is why a travel clinician will ask for a detailed itinerary.

What environmental risks should travellers know about?

Insects and other bites

Mosquitoes, ticks, sandflies and other insects can spread infections. Some mosquitoes bite mainly at night (malaria), while others bite during the day (dengue, Zika and chikungunya). Bite avoidance is important everywhere these infections occur, even where vaccines or tablets are also recommended:

use an effective insect repellent, such as one containing DEET (50% is commonly recommended)
wear long, loose clothing, especially at dawn and dusk
sleep under an insecticide-treated mosquito net if rooms are not screened or air-conditioned

Food, water and sanitation

Where sanitation is limited, infections such as travellers' diarrhoea, hepatitis A, typhoid and cholera are more common. Washing hands, choosing freshly cooked hot food, and drinking bottled, boiled or treated water reduce the risk. Vaccines are available for some of these infections.

Animals

Rabies is present in many countries. Avoid touching dogs, cats, monkeys and bats, and seek medical advice urgently after any bite, scratch or lick on broken skin, even if you were vaccinated before travel.

Altitude

Above about 2,500 metres, altitude sickness becomes more likely. Symptoms include headache, nausea, tiredness and poor sleep, and it can occasionally progress to serious conditions affecting the brain or lungs. Ascending gradually, allowing time to acclimatise and descending if symptoms worsen are the most important measures. Any medicine to help prevent altitude sickness needs an individual assessment by a prescriber.

Heat, humidity and dehydration

Hot climates increase the risk of dehydration, heat exhaustion and heatstroke, particularly for older people, young children and people with long-term conditions or taking certain medicines. Drink plenty of fluids, avoid strenuous activity in the hottest part of the day and seek shade.

Sun exposure

UV radiation is stronger near the equator, at altitude, and near water or snow. Use a broad-spectrum sunscreen with at least SPF 30 and good UVA protection, reapply regularly, and wear a hat and UV-protective sunglasses. Some medicines, including the antimalarial doxycycline, make the skin more sensitive to the sun.

Cold environments

Cold climates and high mountains carry risks of hypothermia and frostbite. Layered clothing, staying dry and planning activities with local conditions in mind help reduce these risks.

Does how I travel and where I stay matter?

Cruises: close living quarters can allow outbreaks of norovirus and respiratory infections, including flu and COVID-19.
Long-haul flights: long periods of sitting slightly increase the risk of deep vein thrombosis (DVT), mainly in people with existing risk factors. Moving around and keeping hydrated help.
Accommodation: camping, hostels and family homes may mean more contact with insects, animals and local food and water than air-conditioned hotels.
Visiting friends and relatives: people visiting family abroad often stay longer and live more like local residents, which can increase exposure. Immunity from childhood does not last, so advice is still important.

Frequently asked questions

Is there malaria at high altitude?

Malaria risk generally falls at higher altitudes, but it is not absent in every high-altitude area. Check the country information on TravelHealthPro and ask your travel clinician.

Which insect repellent is best for travel?

UK guidance recommends DEET-based repellents as first choice for most travellers, including in pregnancy and for children over 2 months. Alternatives exist if DEET is not suitable.

How can I avoid travellers' diarrhoea?

Good hand hygiene, careful food choices and safe drinking water help. Carry oral rehydration salts and seek medical help if you have blood in your stool, a high fever or symptoms that do not settle.

Key takeaways

Climate, altitude, insects, sanitation and accommodation all affect travel health risks.
Bite avoidance, food and water hygiene and sun protection matter on most trips.
Ascend gradually at altitude and descend if symptoms worsen.
A pre-travel risk assessment tailors advice to your trip.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

Want advice tailored to your destination? Book a travel health consultation at Ready Health in Standish, Wigan.