Ant Infestations in London Kitchens: How to Find the Nest and Stop the Trail

Ant calls peak from April through August across London, with a huge spike around the so-called 'flying ant day' in late July. Most are common black garden ants nesting outside and sending foragers indoors. A smaller but trickier subset are Pharaoh ants — a tropical species that's become well established in heated London flats, especially in older blocks.

The problem with ants isn't usually the visible trail. It's the colony you can't see, which can hold tens of thousands of workers and several queens. Spray the trail and you kill foragers; the colony just sends more.

Identify which ant you actually have

Treatment is completely different depending on species, so this is the most important step.

Black garden ant (Lasius niger): 3–5 mm, dark brown to black, single nest outdoors, foragers come in for sugar and protein. By far the most common.
Pharaoh ant (Monomorium pharaonis): tiny (~2 mm), pale yellow-brown, nests indoors in warm voids (behind tiles, in wall cavities, around hot pipes). Multiple queens, multiple satellite nests — sprays cause them to 'bud' into new colonies.
Flying ants: not a separate species — these are the winged reproductives of garden ants during their summer nuptial flight. They don't bite or sting and disappear within days.

Find the trail and follow it back

Garden ants follow chemical pheromone trails between food and nest. Don't disturb the trail at first — watch it. Foragers will lead you to the entry point: a gap under a door, around a pipe, a hairline crack in mortar, or up through an unsealed kitchen plinth.

The nest itself is usually outside, within 5–10 metres of the entry — under paving slabs, in a wall cavity, behind a brick step, or in a flower bed against the wall.

Why shop-bought sprays make it worse

Aerosol ant killers are 'contact' insecticides — they kill the workers they hit and leave a residue that repels the rest. The trail breaks up, foragers stop coming in, and you assume it's worked. The colony is untouched and reroutes within days, often through a different entry. With Pharaoh ants, sprays actively cause budding — the colony splits into multiple new nests and the problem doubles.

The bait approach (what professionals do)

The right approach is the opposite of spraying: you want foragers to find the bait, carry it back, and feed it to the queen and the rest of the colony. The colony dies from the inside out.

Use a slow-acting gel or liquid bait (commonly fipronil or hydramethylnon-based) placed directly on the active trail.
Do not spray, wipe down, or disturb the trail while baiting — you want every forager to find it.
Expect the trail to look worse for 24–48 hours as more workers come to feed. This is a good sign.
Activity should drop sharply within 3–7 days. Full clearance often takes 2–3 weeks.
Once clear, seal the entry point with sealant or a fine wire-wool plug.

Prevention that actually works in a London kitchen

Most repeat ant problems are caused by tiny food sources that the homeowner doesn't think of as 'food.'

Wipe down sticky bottles (honey, syrup, oil) — the lids are usually the attractant.
Empty crumb trays in toasters and air fryers weekly.
Don't leave pet bowls down overnight.
Take out bins nightly during a live infestation.
Seal cracks between worktops and tiles, and around skirting where it meets the floor.

When to call a professional

Garden ants in a single kitchen usually clear with disciplined home baiting. Bring in a pro if: you have ants in multiple rooms, you suspect Pharaoh ants (especially in a flat with shared heating), the trail keeps reappearing in a new spot after baiting, or you can hear/see activity inside the wall itself. Pharaoh ant treatment in particular needs a coordinated bait programme — often building-wide — and is one job we'd push you toward a licensed controller for.

Frequently asked questions

Why have ants suddenly appeared in spring?

Garden ant colonies overwinter underground and become active again once soil temperatures hit around 10°C — usually March–April in London. Foragers immediately start scouting for food sources and find any tiny gap into the kitchen.

Are ants in the kitchen a health risk?

Garden ants are mostly a nuisance, though any insect on food prep surfaces is undesirable. Pharaoh ants are a genuine concern — they're known to transfer pathogens including Salmonella and are taken seriously in hospitals and food premises.

Will pouring boiling water on the nest work?

It kills the visible workers and a small portion of the colony. The queen, eggs and most of the brood are deeper than boiling water can reach, and the colony recovers within weeks. Bait works better and is far less messy.