Fleas bite people, but do not settle on them
The cat flea, which causes nearly every household flea problem, will happily bite a person when there is nothing else around. It does not stay on us, though, and people are a poor host for keeping a population going. Without an animal in the home, a flea problem will not last for ever — but the eggs, larvae and cocoons already in the floor can keep producing hungry adults for some time.
An animal that used to live there
This is the most common explanation. A cat or dog that belonged to the previous owner or tenant left eggs in the carpets. The larvae grew, spun cocoons and then waited. Cocoons can sit for weeks, and the adults inside hatch when they sense vibration, warmth and the carbon dioxide in our breath. Nobody walking around means nothing hatches; someone moving in means a sudden wave of biting fleas.
People moving house are the ones who usually discover this — Cricklewood is a good example of an area where homes change hands often. The first weeks are covered in flea problems after moving into a new home.
Cats that call in
A neighbour's cat that slips through an open back door, uses a cat flap left behind by previous owners, or naps on a garden chair can drop flea eggs as it goes. So can a stray sheltering under a shed. If you have noticed a cat treating your home or garden as its own, that may be the link.
Foxes and the garden
Foxes can carry fleas, and a fox that rests under decking or behind a shed can leave eggs in that shady spot. This is less likely to cause bites inside than a cat indoors, but a den right beside a back door or a conservatory is worth keeping in mind if the bites start after time spent in the garden.
Birds and animals in the roof
Birds nesting in the eaves or a loft have their own fleas. When the young birds leave, those fleas can wander in search of a new host, and some find their way into top-floor rooms. Squirrels in a roof space carry fleas too. If you hear scratching overhead as well, read how to know if squirrels are in your loft.
Picking them up elsewhere
Looking after a friend's dog, visiting a home that has fleas, or handling an animal at work can bring the odd flea back on clothing or a bag. A single stray is unlikely to start a lasting problem in a home with no animals, but it can explain one or two bites that stop on their own.
Shared houses
In a shared house, one housemate's pet, or a pet that has since moved out with a former tenant, can affect every room with a carpet. Shared houses and HMOs in areas like Kilburn often have several people coming and going, so talk to the others and to the landlord before assuming the problem is only in your room.
When it is not fleas
If no flea ever turns up on a white sock and there is no flea dirt, look at other causes. Bites in lines on the arms, neck or shoulders after a night's sleep suggest bed bugs — see the first signs of bed bugs. The checks for fleas are in how to know if you have fleas.
Getting the house treated
No pet does not mean no treatment: the stages in the floor still need dealing with. Flea treatment in Brent costs £180 for the first room and £60 for each additional room, so a flat with a living room and two bedrooms affected would be £300. Book flea treatment and tell us that there are no animals in the home.
