Mosquito Protection in Thailand: What Works and What Doesn't

Mosquitoes in Thailand fall into two categories: the daytime Aedes aegypti mosquito (dengue fever carrier — active dawn to dusk) and the nighttime Anopheles mosquito (malaria carrier — active dusk to dawn). Dengue is the bigger risk for most travellers, with outbreaks occurring year-round but peaking in the rainy season (June–October). Malaria risk for most tourist areas is very low — primarily a concern in forested border areas near Myanmar and Cambodia, not in Bangkok, beach resorts, or major tourist destinations. It is worth noting that Aedes mosquitoes are active through the day, not just at the dusk-and-dawn hours most travellers instinctively guard against, so applying repellent only in the evening leaves the actual dengue risk largely unmanaged.

The most effective protection: DEET-based repellent at 30–50% concentration applied to all exposed skin, especially ankles and feet (where Aedes mosquitoes prefer to bite). Reapply every 3–4 hours. Alternatives: Picaridin (equally effective, less skin irritation) and lemon eucalyptus oil (effective but shorter duration). Local Thai brands like Soffell and Shieldtox (DEET-based) are available everywhere for ฿30–60. Apply repellent after sunscreen, never mixed into the same layer, and keep it away from a child's hands and mouth, since young children tend to touch their faces without thinking. Clothing treated with permethrin, sold as a spray or as pre-treated garments in most outdoor shops, adds a second layer of protection that survives several washes and is a sensible addition for a longer trip through forested or rural areas.

Accommodation precautions: check for holes in window screens, use air-conditioning (mosquitoes dislike cold), or sleep under a mosquito net in budget guesthouses without AC. Citronella candles and coils provide some protection in outdoor areas, though they are noticeably weaker than DEET and better treated as a background measure than your main defence over dinner — most open-air restaurants and beach bars run plug-in or table-top repellent units for exactly this reason, and staff will usually refill or reposition one if you ask. Standing water is the other side of the equation — a bottle cap or a neglected plant saucer is enough for Aedes to breed in, so anyone staying somewhere for weeks rather than days is doing their neighbours a favour by tipping out anything that collects rain.

Wear long sleeves and ankle-covering clothing at dawn and dusk. Children and older travellers are worth being a little more conservative with, both because sunscreen and repellent layering is easy to get wrong on a child's smaller frame and because a second dengue infection in someone previously exposed carries a meaningfully higher risk of a severe case than a first one — a detail worth mentioning to a doctor if you have had dengue before and develop symptoms again. If you develop sudden high fever within 14 days of visiting Thailand, seek medical attention immediately and mention you have been in a mosquito-endemic area.