Insect bites in Thailand: mosquitoes, sand flies, itch relief and warning signs
Insect bites in Thailand are part of island life: mosquitoes around dusk and sand flies on some beaches. Most bites are just itchy and settle in a few days. The things that matter are avoiding bites in the first place, not scratching them into an infection, and seeing a doctor if you get a fever.
The short version
Insect bites in five points
- Use a proper repellent on exposed skin, especially from late afternoon, and put it on after sunscreen.
- Cover up in the evening and sleep under a net or in an air-conditioned room with closed screens.
- Don’t scratch: wash bites, cool them, and ask a pharmacist about itch relief.
- Watch for infection: a bite that gets hotter, redder, more swollen or painful, or weeps pus.
- Fever after bites in Thailand means a doctor, not waiting it out.
What bites on Koh Phi Phi?
Two culprits cause most of the itchy bites travellers complain about:
- Mosquitoes: found across Thailand, indoors and out. Some types bite mainly around dawn and dusk, others during the day, so there isn’t one “safe” time.
- Sand flies (sometimes called sand fleas or no-see-ums): tiny biting insects found on some beaches, often around wet sand, seaweed and the high-tide line, especially early and late in the day. You often don’t feel the bite, then find a cluster of very itchy red spots on your ankles and legs hours later.
Ants, bed bugs and the occasional wasp or bee are possible too. Most bites, whatever caused them, are small, raised and itchy, and get better in a few days.
How to avoid mosquito bites in Thailand
The US Centers for Disease Control and Prevention (CDC) recommends using a registered insect repellent with one of these active ingredients: DEET, picaridin (also called icaridin), IR3535 or oil of lemon eucalyptus. Pharmacies and many convenience stores in Thailand sell repellent sprays and lotions; check the label for one of these ingredients and follow the instructions on the pack.
- Sunscreen first, repellent second: the CDC advises putting repellent on after sunscreen.
- Reapply after swimming or heavy sweating, following the label.
- Cover up in the evening with light long sleeves and long trousers or a sarong.
- Sleep protected: an air-conditioned room with closed windows and screens, or under a mosquito net. Ask your bungalow for a net if there isn’t one.
- Use repellent on children correctly: the CDC says not to use oil of lemon eucalyptus products on children under 3, so check the label and ask a pharmacist for a suitable product.
Sand flies in Thailand: how to avoid the bites
Sand fly bites can be maddeningly itchy, and because they often come in clusters, scratching is tempting. To reduce them:
- Sit on a sun lounger or a thick towel rather than directly on damp sand, especially early and late in the day.
- Use repellent on your legs and ankles on the beach as well as in the evening.
- Ask locally: sand flies tend to be worse on some beaches and at some times than others, and hotel staff or boat crews usually know where.
- Rinse off sand after the beach and cover your legs if you notice bites starting.
Insect bite treatment in Thailand: easing the itch
The NHS advice for an ordinary bite is simple:
- Wash the bite with soap and water to lower the chance of infection.
- Cool it with an ice pack wrapped in a cloth, or a clean cloth soaked in cold water, for at least 20 minutes if it’s swollen.
- Raise the area if you can, for example propping up your feet for ankle bites.
- Don’t scratch: broken skin in a hot, humid climate gets infected easily.
- Skip home remedies such as bicarbonate of soda, which the NHS advises against.
If the itching is bad, ask a pharmacist. In Thailand, as in the UK, they can suggest itch-relief creams or tablets that suit you. Tell them about any other medicines, allergies, pregnancy, or if it’s for a child. You will find basic after-bite products in most 7-Eleven stores, but a pharmacist can give better advice for a lot of bites or a bad reaction.
When you need a doctor, not a cream
A fever after insect bites in Thailand needs a doctor, even if the bites themselves look fine, because mosquitoes in Thailand can spread infections such as dengue. See a doctor too if a bite becomes hot, red, swollen and more painful, weeps pus, has a red area that is spreading, or if you feel unwell with swollen glands, which can mean an infection. Call 1669 (Thailand emergency medical services) straight away for swelling of the lips, mouth, tongue or throat, difficulty breathing or swallowing, feeling faint or suddenly very confused or drowsy: this can be a severe allergic reaction. Our guide to medical help on Koh Phi Phi lists the clinics and how to reach the mainland.
Infected insect bites: what to look for
In a hot, humid place, scratched bites are one of the most common reasons travellers end up at a clinic. The NHS lists the signs to look out for: skin around the bite that feels hot or looks red (redness can be harder to see on brown or black skin), pain, swelling, and pus or fluid coming out. A spreading area of painful, hot, swollen skin can be cellulitis, a skin infection that needs treating quickly.
If you notice any of these, don’t wait until you get home. A pharmacist or doctor can look at it and decide on treatment. Keep the area clean and covered while you sort it out, and avoid swimming in the sea with an open, weeping wound.
Can an IV drip help with insect bites?
No. An IV drip doesn’t treat bites, itching or infections, and if you have a fever you should see a doctor first rather than book a drip. If you are run down and struggling to eat and drink after a doctor has seen you, our nurses can talk through whether a drip makes sense, but most bites only need the simple care above. Our guide to heat rash in Thailand may help if your spots look more like prickly heat than bites.
Insect bites FAQ
Bites in Thailand: your questions
How long do mosquito bites last?
Most bites are itchy for a day or two and fade within a few days. Scratching makes them last longer and can lead to infection.
Are sand fly bites dangerous?
Usually they’re just very itchy. The main risk is infection from scratching. See a pharmacist or doctor if a bite looks infected or you feel unwell.
What repellent should I use in Thailand?
The CDC recommends products with DEET, picaridin (icaridin), IR3535 or oil of lemon eucalyptus. Follow the label, put it on after sunscreen, and ask a pharmacist for a suitable product for children.
Do I need a mosquito net on Phi Phi?
An air-conditioned room with closed windows and screens is fine. If your room has open windows or gaps, a net makes a real difference to bites at night.
I have a fever and lots of bites. What should I do?
See a doctor. In Thailand a fever after mosquito bites can be dengue or another infection that needs a blood test. If you have warning signs like trouble breathing or confusion, call 1669.
Keep reading
Staying well on Phi Phi
See our guide to medical help on Koh Phi Phi for clinics and pharmacies, or heat rash in Thailand for other itchy spots.
Sources: NHS: Insect bites and stings · CDC: Prevent bug bites · NHS: Cellulitis · WHO: Dengue and severe dengue. Last updated October 2026.
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