Why do I still get mosquito bites with the windows shut?

Shutting the windows at night helps, but mosquitoes do not only come in at night. They fly in during the day through an open door or window, rest on a wall or behind a curtain, then come out to feed once you are lying still in bed. Some also breed indoors, in a plant saucer or a vase. So the fix is to find the way in, find any water, and make the bed hard to reach.

Waking up bitten every morning wears you down. It is also worth checking it really is mosquitoes, because several night biters leave bites that look alike.

Is it mosquitoes?

• Mosquito bites: itchy raised lumps on skin that was uncovered, like the face, arms and feet. You may hear a whine near your ear.
• Bed bug bites: often on skin that touched the mattress, with dark spots on the sheets or in the seams. See marks on my sheets: could it be bed bugs?
• Flea bites: small, very itchy and often round the ankles and lower legs. See fleas but no pets.

Before bed, check the walls and ceiling with a torch. Mosquitoes rest still on walls, often high up and in dark corners. If you find them, you have your answer, and you can deal with them before you sleep.

How they are getting in

• Doors left open in the heat. This is the big one. A fly screen for the door, or a magnetic screen curtain, lets air in and keeps mosquitoes out.
• Windows opened even briefly, gaps in frames, and vents or extractor ducts without mesh.
• Gaps under outside doors. A door sweep closes them. See sealing gaps.
• The next room. A shut bedroom window does not help much if the window next door is open and the door between is too.

Are they breeding indoors?

Mosquitoes lay eggs on still water, and some kinds need very little. Look for:

• Saucers under plant pots, and pots without drainage.
• Vases where the water is not changed.
• The drip tray under the fridge, if yours has one.
• Buckets, pet bowls left for days, and water sitting in a sink, shower or toilet you rarely use.

Change vase and bowl water often, empty saucers, and run taps or flush in rooms you hardly use. Outside, tip out standing water near the house too. There is more on that in keeping mosquitoes away without chemical sprays.

Protect the bed tonight

1. Hunt before you sleep. Torch round the walls and ceiling, and swat or vacuum any you find.
2. Use a bed net. A fine mesh net with no holes, tucked under the mattress, is one of the most reliable barriers there is. For a cot, use one made for cots.
3. Keep the fan on and aimed at you. Mosquitoes are weak fliers, and moving air makes it hard for them to land. Your fan was a good start.
4. Keep the bedroom door shut in the evening, and lights low near any open window.

If you want a repellent on your skin, use one made for the purpose and follow the label, including any age limits for children. Plug-in devices that release insecticide are regulated: follow the label and check they are allowed where you live. Ultrasonic plug-ins and phone apps are not a fix. They do not keep mosquitoes away.

Health: where mosquitoes carry illness, follow your local health service’s advice first. If you get a fever or feel unwell after bites, especially after travel, see a doctor and tell them where you have been. For bites that swell a lot, ask a pharmacist.

Still bitten after all that?

If the doors are screened, there is no water indoors and you sleep under a net, but bites still appear, go back to the first question. Catch the culprit in a glass or on a sticky trap and photograph it. Bites under a sealed net point away from mosquitoes and towards something in the bed itself.

If mosquitoes are breeding somewhere you cannot reach, like a neglected pool or a blocked public drain nearby, report it to your local council or health authority. Our mosquito guide has more on where they breed.