How many treatments you need

Why eggs determine the number of treatments

Insect eggs are protected by a tough shell that most insecticides cannot get through. That means a treatment kills every living insect present but leaves the eggs intact.

After 7-14 days a new generation hatches. If the treatment had no residual action, or that residual layer was washed off, the population rebuilds — and to the person living there it looks as though the treatment did nothing.

There are two solutions: a product with long residual action that is still active when the eggs hatch, or a second treatment timed for exactly that window. Often both, because the two reinforce each other.

How many treatments by species

A repeat treatment costs from €60. Where a second visit is expected we say so before the first one rather than after it.

Why 10 to 14 days specifically

The interval is not arbitrary. It is chosen so the second treatment lands at the point where the larvae hatched from eggs have already hatched but have not yet reached breeding age and have not laid eggs of their own.

Treat earlier and some eggs have not hatched, so the cycle simply repeats. Treat later and the new generation has already bred, and you are back at the start.

This is also why moving a scheduled second treatment by a week is not a neutral change. If the date has to shift, tell us, because the plan may need adjusting rather than just delaying.

Preparing for the second treatment

If a second visit is scheduled, preparing for it is simpler than for the first, but a few steps matter.

• Do not do a deep clean in between. This is the single most common way a two-stage plan gets undermined. The residual layer has to survive until the second visit.
• Do not re-wash textiles that were washed for the first treatment and kept sealed. Once is enough.
• Do pull the furniture out again so the same areas are reachable.
• Do note where you have seen activity since the first visit. It tells us where to concentrate.

See what to do after treatment for the full list.

When a third treatment is needed

A third treatment usually points not to a resistant pest but to one of these circumstances:

• the source is in a neighbour's flat and reinfestation is continuous;
• a harbourage was never found — in a drain trap, in a floor void, in one forgotten packet;
• the residual layer was washed off a couple of days after the treatment;
• preparation was incomplete and part of the property was effectively untreated.

Which of these it is changes what should be done next, so repeating the same work without establishing the cause would most likely produce the same outcome. See why pests come back.

How to tell whether it worked

Judging the result in the first few days is misleading, because activity can actually increase then. The practical criteria are these.

• Bedbugs. No new bites in the morning for 10-14 consecutive days, and no fresh dark spots on the sheet.
• Cockroaches. No sightings when you turn the kitchen light on at night, over two weeks. That is the honest test, not the daytime one.
• Fleas. No new bites on the ankles, and the animal has stopped scratching after its vet treatment.
• Moths. No adults flying at dusk and no new webbing in the affected cupboard after a month.

Isolated individuals in weeks one and two are expected and not a failure. Unchanged activity after 3-4 weeks is.

It is worth saying plainly that a second treatment is not an admission that the first one failed, and it is not an upsell. For bedbugs and fleas it is the standard shape of the job, built into the plan from the start because of how those species reproduce. A provider who promises to clear an established bedbug infestation in a single chemical visit is either using heat, or is not being straight with you about the eggs.

Where we can genuinely say one visit is likely — a wasp nest, an ant colony reached by bait, most gel bait cockroach jobs — we say so, and we do not add a second visit that would achieve nothing.