Mosquitoes and Sandflies on Koh Phangan: What Actually Works

The honest version

Koh Phangan is a tropical island with jungle in the middle of it, and there are insects. Not clouds of them, not the kind that drive you indoors at six o'clock, but enough that the people who have a good time here are the ones who thought about it for ten minutes before they arrived.

Most visitors come away with a handful of itchy spots on their ankles. A few come away with thirty, having spent an evening sitting on wet sand at dusk in shorts. The difference is almost entirely about timing, location and one small bottle bought at a convenience shop.

When mosquitoes actually bite

Two broad groups matter here, and they keep different hours.

The mosquito that carries dengue is a daytime biter, most active in the hours after sunrise and in the last couple of hours before dark. It is a low flyer and goes for ankles and calves. It breeds in small containers of clean standing water — plant saucers, buckets, a forgotten cup on a terrace — rather than in the sea or in fast-running streams. After heavy rain, the number of these containers across the island quietly multiplies for about a week.

The other group comes out properly after dark, prefers still air and shaded, damp ground, and is the reason an unscreened bungalow near a canal is a different experience from a room on a ridge with the fan on.

A few things follow from this that are more useful than any spray:

• Moving air is a real deterrent. A fan on a terrace, or a position that catches the afternoon wind, does more than most people expect.
• Dusk is the hour to cover your legs. Thin trousers beat any repellent.
• Standing water near where you sleep is worth two minutes of attention. Tip out saucers and buckets after rain.

On dengue itself, the national picture in 2026 has been better than the year before: Thailand's Department of Disease Control reported about 21,600 cases and 31 deaths up to late August, and weekly case counts through mid-year ran far below 2025 levels. It remains a real illness and the seasonal peak sits in the rainy months, which is where we are now. What to do if you do fall ill is covered in the journal's piece on medical care on the island.

What to buy once you are here

Do not bother carrying repellent halfway around the world. Every 7-Eleven in Thong Sala, Srithanu and Baan Tai stocks the two Thai brands everyone uses — Sketolene and Soffell — for a fraction of what a European pharmacy charges. Sketolene Shield is the 20% DEET version and is the one to take into the jungle or out at dusk; the milder, sweet-smelling bottles are fine for a day around a pool.

Buy the spray rather than the cream if you are putting it on over sunscreen. Repellent goes on after sunscreen, not before.

Coils and plug-in vaporisers are sold in the same shops and are standard in Thai households. A coil burning quietly at the upwind end of a terrace during dinner works well outdoors. Indoors, a fan and a closed screen door usually do the job on their own.

Sandflies are a beach problem, not a jungle one

Sandflies are the ones that genuinely ruin holidays, because people do not see them coming. They are tiny, they live on the beach itself, and they prefer damp sand. They are at their worst in the late afternoon, on stretches of beach sheltered from the wind, and they will bite you standing in shallow water — being wet is no protection at all. Reports from across southern Thailand put the end of the dry season as the worst stretch.

You often do not feel the bite. The itch arrives hours later and can last for days, longer than a mosquito bite, and the welts are harder to leave alone.

Practically, on Phangan that means:

• Enclosed, wind-sheltered bays are more likely to have them than open west-coast beaches with an afternoon breeze.
• Sitting directly on damp sand at sunset is the classic way to collect twenty bites. A towel on dry sand, a sarong, or a chair changes the odds considerably.
• Repellent on feet, ankles and the backs of legs is the part people forget. That is where almost all sandfly bites land.

If a beach turns out to be bad on one evening, it will probably be bad the next evening too. Move along the coast rather than persevering.

Ants, centipedes and the night shift

Ants are the daily reality of any house with trees around it, and they are harmless. Keep fruit covered and sugar in a sealed jar and you will barely notice them.

Centipedes are the ones worth a word. The big Scolopendra species come out in wet weather and occasionally come indoors. The bite is genuinely painful, with swelling and redness, but for a healthy adult it is rarely dangerous. Thai hospital guidance and a Bangkok hospital study point the same way on first aid: clean the site, use warm or hot water immersion rather than ice for the pain, take ordinary painkillers, and get help if there is any sign of an allergic reaction. Shake out shoes left outside overnight in the rainy season and you will almost certainly never meet one.

When a bite stops being a nuisance

Scratched bites get infected easily in this climate, and an infected bite on an ankle after four days of sea swimming is one of the more common reasons visitors end up at a clinic. Clean broken skin with antiseptic, keep it covered when you swim, and buy an antihistamine cream from any pharmacy in Thong Sala rather than waiting it out. A bite that is spreading, hot and red rather than simply itchy needs a doctor, not patience.

Where you sleep matters most

If this all sounds like a lot, consider that two of these three problems are tied to specific places at specific hours: wet sand in the late afternoon, and still air after dark. Height and wind solve a surprising amount. Ullassa sits on a hilltop above Maduawan with the west wind coming across the terrace most afternoons, which is a quieter arrangement than it sounds — and still worth a bottle of Sketolene in the bag for sunset on the beach at Hin Kong, ten minutes down the hill.