Ants are pouring out of my skirting board. What do I do?

Breathe. A sudden stream of ants from one gap is a normal ant pattern, not a sign your home is overrun. Usually a nest in the wall or under the floor has found food, or the winged ants are leaving on a mating flight. Both can be handled. Today is about clearing them and taking food away. The nest is dealt with over the next week or two, with bait, not spray.

What is going on

• Wingless ants in a line are workers. A scout found food and marked the way, and the rest followed.
• Winged ants are a mating flight. They leave the nest together, often on warm, humid days, and the flight is short. More on that in flying ants in the house.
• Both from the same gap means the nest is close: inside the wall, under the floorboards, or around an old fireplace.

Today

1. Vacuum the ants you can see, winged ones too. Empty the bag or bin outside.
2. Wipe the trail with warm soapy water. That clears the scent the others follow. No need for bleach.
3. Put food away. Sweet things in sealed tubs or the fridge, crumbs swept, the bin emptied, the cat’s bowl lifted between meals.
4. Note the exact gap they come from. Take a photo. That is where the bait goes, and later the sealant.

Then bait, do not spray

Spraying the ants you see feels like action, and it does kill those ants. But they are the few the nest sent out. The queen and the rest stay in the wall and send more. Some kinds of ant even split into new nests when sprayed.

Bait works the other way round. Workers eat it and carry it home, so it reaches the nest. Place enclosed ant bait stations on the trail, close to the gap. Then leave the trail alone around them: do not wipe it or spray near the stations.

Expect more ants for a few days. That is the bait working, not failing. Follow the label on the product, and check it is allowed where you live. If they walk straight past it, see ants that ignore bait.

Kids and pets: use enclosed stations, tucked behind heavy furniture, out of reach of children and pets. Loose ant powder along a skirting board is easy for a cat to walk through and lick off its paws, so leave it out. If you cannot place a product out of reach, do not use it. More in ant bait with a baby or pets.

If you are going away in two days

• Put the stations down now, so the ants have time to find them while you are still home to check.
• Leave the kitchen bare: food sealed, bin empty, no dishes in the sink.
• Brief whoever feeds the cat. Lift the bowl after each meal, leave the stations where they are, and no spraying.
• When you get back, vacuum any dead winged ants and look at the trail. Fewer ants means the bait is reaching the nest.

Seal the gap once it goes quiet

When you have seen no ants for a while, fill the gap with a suitable sealant. Not before: sealing a busy gap can push them out of a different one. Our guide to sealing gaps shows how.

When to get help

• Ants are still streaming out after a few weeks of bait.
• The wood near the gap is soft, damp or crumbly. See carpenter ants.
• The winged insects have straight antennae and a thick waist. They could be termites, so ask a professional to look.
• You rent. Tell your landlord in writing, with the date and a photo.

The ant guide has the full plan.