It bites and feeds on blood. For most people the result is itching and nothing more, though fleas can transmit tapeworm to pets and, rarely, infections to people. The pet is the reservoir; the home is where the population actually lives.
We identify, we don't diagnose. If you've been bitten or stung and symptoms develop, or you're worried, seek medical attention.
Size2–3 mm
MarkingsFlattened side to side, so it looks narrow from above and tall from the side · Dark reddish-brown, 2–3 mm, with no wings
WhereOn the animal for feeding; in carpet, bedding, upholstery and floor cracks for everything else.
How to tell it apart
Flattened side to side, so it looks narrow from above and tall from the side
Dark reddish-brown, 2–3 mm, with no wings
Enormous hind legs and a jump that is unmistakable
Very hard to crush between fingers — the body is armoured
Black specks on the animal or its bedding that bleed rust-red on wet tissue
Where you’ll find it
Across the United States. The cat flea is the species on both cats and dogs.
On the animal for feeding; in carpet, bedding, upholstery and floor cracks for everything else.
How it behaves
The critical fact for anyone trying to deal with them is that most of the population is not on the pet. Adults feed on the animal, but eggs are not sticky and drop off into carpet and bedding, where larvae and pupae develop out of sight. Treating only the animal therefore leaves the majority of the infestation in place. Pupae can also wait a long time and hatch in response to vibration and warmth, which is why a house left empty can produce a sudden wave of fleas when someone returns.
What a bite looks like
Small red spots, often with a darker centre, usually in clusters around ankles and lower legs. Some people react strongly and some barely at all.
A sharp small itch, immediate rather than delayed, and persistent for several days.
We identify, we don't diagnose. Bites usually need nothing more than not scratching. See a doctor for signs of infection, or for a severe or spreading reaction.
A skin mark cannot confirm which animal caused it. Read the bug bite and sting guide for the limits and the symptoms that should end an online search.
You’ve found one indoors
Treat the animal and the environment at the same time, or it recurs. Vacuum thoroughly and often — it removes eggs and larvae and the vibration triggers pupae to hatch where they can be dealt with — and wash pet bedding hot. Veterinary advice on the animal's treatment is worth having rather than guessing at products.
Common questions
What is flea dirt, and how do I test for it?
Flea droppings — digested blood. Comb some onto damp white tissue: if it smears rust-red, it is flea dirt and you have fleas. Ordinary dirt stays dark. It is the most useful ten-second test in this category.
Why do the bites stop at my ankles?
Fleas live in floor coverings and jump upward a limited distance. Ankle and lower-leg clusters are close to diagnostic, and they distinguish flea bites from bed bug bites, which appear on whatever is exposed while you sleep.
I treated the pet and they came back. Why?
Because most of the population was never on the pet. Eggs, larvae and pupae are in the carpet and bedding, and the environment has to be treated alongside the animal.
Can I get fleas without a pet?
Yes, though it is less common. They arrive on wildlife, from a previous occupant's infestation, or on clothing, and cat fleas will bite people readily when no animal host is available.
Justin Williams · CC-BY