Heading abroad soon? Before you pack, it's worth clearing up a few travel health myths you might have come across.
Some are fairly harmless. Others can leave you unprotected against genuinely serious risks, like malaria and blood clots. Here are five myths worth setting straight before you head off.
Myth 1: You only need to take anti-malaria tablets while you're actually abroad
This one catches out more travellers than you'd think, and it's a serious mistake. You can still be at risk of malaria after you've left a risk area. That's why most antimalarial tablets need to be continued after you get home.1
Exactly how long depends on your tablet. Malarone (atovaquone and proguanil) is taken for 7 more days after you leave the risk area.2 Doxycycline and mefloquine (Lariam) are taken for 4 more weeks.3,4 Malarone also has activity against the early liver stage of the parasite.2
Malaria symptoms usually appear 7 to 18 days after a bite. But sometimes they take months, and rarely years.1 If you feel unwell within a year of coming home, tell a doctor about your travel, even if you finished your course exactly as prescribed.1
Fever, sweats or flu-like symptoms after a trip to a malaria area need urgent medical help. Make sure you say where you've been.
Not sure which antimalarial suits your trip? Our guide to choosing the right antimalaria tablet is a good place to start. The NHS advises asking for advice at least 4 to 6 weeks before you travel, though you can still get help at the last minute.1
Myth 2: Mosquito bites are only something to worry about after dark
It's true that Anopheles mosquitoes, the type that spreads malaria, are more active from dusk to dawn. But that's not the whole story. Some mosquitoes bite during the day.5
Aedes mosquitoes bite in daylight, and they can spread dengue, chikungunya, Zika and yellow fever.5 So you'll need to guard against bites throughout the day, not just at night. Bites can happen indoors as well as outdoors.5
Stagnant or standing water is where mosquitoes are likely to breed, so it's worth steering clear of it where you can.5
“Mosquito protection is not just a night-time precaution. Some mosquitoes that spread infections bite during daylight, so protection needs to match your destination's risks throughout the day and night. Use an appropriate repellent as directed, cover exposed skin and, when using sunscreen too, apply sunscreen before repellent.
Ana Carolina GoncalvesSuperintendent Pharmacist
That means repellent, covered skin and mosquito nets all matter, whether you're heading out for breakfast or an evening walk. The NHS recommends a 50% DEET-based repellent on your skin, and sleeping under insecticide-treated nets in a malaria area.1 If you're travelling somewhere with malaria, keep taking your prescribed antimalarial tablets too.
Wearing sun cream as well? Put it on first, then apply your repellent on top.
Myth 3: Sticking to bottled water means you won't get traveller's diarrhoea
Traveller's diarrhoea affects over 1 in 5 people visiting high-risk destinations. It's usually caused by bacteria, and sometimes a virus or a parasite, picked up from contaminated food or water.6
Bottled water is a sensible precaution. But there are plenty of other ways to pick up a stomach bug, like ice cubes, or salads and vegetables washed in tap water.7
Peel it, cook it or leave it. A simple rule for fruit, salads and street food.
Food that's been left uncovered in warm places, like buffets, is a common culprit too. So is raw or undercooked meat and fish.7 And so is not washing your hands before you eat.6
Most cases are mild and settle on their own in three to four days. Rest, fluids and a rehydration sachet such as Dioralyte can help.6
See a doctor if you're not improving within three days. Get medical help straight away if you have a fever of 38°C or more, blood or mucus in your poo, or severe tummy pain. Children, older people and anyone who can't keep fluids down or shows signs of dehydration should get advice sooner.7
Myth 4: Jet lag will just sort itself out if you get enough sleep
Jet lag happens when your body clock is out of step with local time. It usually improves within a few days as your body adjusts, but sleep alone isn't the whole answer.8
What helps most is moving to the new time zone's schedule as quickly as you can. The NHS suggests going outside in daylight, sleeping only at night and not napping in the day.8 It's also best to go easy on caffeine and alcohol on the flight.8
Melatonin is a prescription-only medicine in the UK.9 The NHS says there's some evidence that it makes symptoms less severe and can shorten recovery time after a long flight by a day to a day and a half, but it may not be available on NHS prescription.9
The usual adult dose is one 3mg tablet at your normal bedtime once you've arrived, for up to five nights. Do not take it before 8pm or after 4am local time.10
Daylight and a new sleep schedule do a lot of the work. Try getting outside at your destination as soon as you can.
Melatonin can make you drowsy. Do not drive, ride a bike or use machinery if you feel sleepy, dizzy or unable to concentrate after taking it.9
Pharmica's melatonin consultation is for jet lag, not general sleep problems. Take it only between 8pm and 4am, for no more than 5 days. Avoid alcohol, and do not drive or use heavy machinery for at least 8 hours afterwards.
Melatonin tablets are available from Pharmica if a prescriber confirms they're suitable for you, after a short online consultation.
Myth 5: Only older travellers need to worry about DVT on flights
Deep vein thrombosis (DVT) tends to get filed away as something only older travellers, or people with health conditions, need to think about. In reality, a long trip is a risk factor in itself, whatever your age.
The NHS lists trips of more than 4 hours by plane, car or train as a time when you have a higher chance of DVT.11 It's also more likely if you're dehydrated.11
Some things push that risk higher. These include being pregnant, having had surgery, taking HRT or an oestrogen-containing contraceptive such as the combined pill, living with overweight or obesity, and having had a DVT before.11 If any apply to you, speak to a GP or pharmacist before a long trip.
On a long trip, get up and move around every hour or so when you can. Wear loose clothing, drink plenty of water and avoid alcohol.11
Pain or swelling in one leg, often in the calf, after a trip needs urgent attention. Ask for an urgent GP appointment or call NHS 111.11 Call 999 if you also feel short of breath or have chest pain.11
A painful, swollen leg with breathlessness or chest pain after a flight could mean a clot has reached your lungs. Call 999 straight away.
Our travel health kit guide covers what else to pack for a long-haul trip.
Frequently asked questions
Do I need anti-malaria tablets for the whole country, or just certain areas?
Risk can vary hugely within a single country, so it isn't simply a case of this country, yes, or that country, no. A pharmacist or travel clinic will look at your exact itinerary, including which regions you're visiting and the time of year. They can then work out whether antimalarials are recommended and which one suits your trip. Check your destination on the TravelHealthPro website before you go.
How do I protect myself from mosquito bites during the day?
Use a repellent with 50% DEET on exposed skin. Higher strengths don't protect for longer. Follow the label for age limits and reapplication, and put sun cream on first. Cover up with loose, long clothing where practical, sleep under insecticide-treated nets in malaria areas, and avoid standing water, where mosquitoes breed. Day-biting mosquitoes can bite indoors as well as outdoors.
When should I see a doctor about traveller's diarrhoea?
Most cases are mild and settle on their own in three to four days with rest and fluids. See a doctor if you're not improving within three days. Get medical help straight away if you have a fever of 38°C or more, blood or mucus in your poo, or severe tummy pain. Seek advice earlier for children, older people, or if you show signs of dehydration.
How long does jet lag usually last?
Jet lag usually improves within a few days as your body clock adjusts to the new time zone. You can help it along by switching to local time quickly, getting outside in daylight, sleeping only at night and avoiding too much caffeine and alcohol.
Is the increased DVT risk only linked to long-haul flights?
No. The NHS lists journeys of more than four hours by plane, car or train as a time when you have a higher chance of DVT, so it isn't limited to long-haul flying. Get up and move around every hour or so when you can, wear loose clothing and drink plenty of water. Get urgent advice if one leg becomes painful or swollen.
References
- NHS. Malaria. NHS website; 2025. nhs.uk
- Glaxo Wellcome UK Ltd trading as GlaxoSmithKline UK. Malarone 250 mg/100 mg film-coated tablets: Summary of Product Characteristics. Electronic Medicines Compendium; 2026. medicines.org.uk/emc
- Waymade Plc trading as Sovereign Medical. Doxycycline 100mg capsules: Summary of Product Characteristics. Electronic Medicines Compendium; 2026. medicines.org.uk/emc
- Neon Healthcare Ltd. Lariam 250 mg tablets: Summary of Product Characteristics. Electronic Medicines Compendium; 2022. medicines.org.uk/emc
- TravelHealthPro (National Travel Health Network and Centre). Insect and tick bite avoidance. TravelHealthPro; 2026. travelhealthpro.org.uk
- TravelHealthPro (National Travel Health Network and Centre). Travellers' diarrhoea. TravelHealthPro; 2024. travelhealthpro.org.uk
- TravelHealthPro (National Travel Health Network and Centre). Food and water hygiene. TravelHealthPro; 2025. travelhealthpro.org.uk
- NHS. Jet lag. NHS website; 2023. nhs.uk
- NHS. Melatonin: common questions. NHS website; 2023. nhs.uk
- NHS. How and when to take melatonin. NHS website; 2023. nhs.uk
- NHS. DVT (deep vein thrombosis). NHS website; 2026. nhs.uk
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.