How do I know if my cat has fleas

Updated April 3, 2020

Why is it so hard to know?:

Why Can’t We See Fleas?

flea dirt in a cat
  • Cats are very good at removing flea evidence
  • Fleas are fast runners
  • Cats have thick coats, and
  • Adult flea numbers are often very low

The funny thing about this very good question is that we almost never get asked How do I tell if my DOG has fleas? Read here about how even vets are fooled into thinking dogs don’t have a flea problem.

Here’s what often happens. A cat comes to us for either a problem or a routine preventative, and we (as always) perform a full physical exam. There is usually no mention of fleas but as you are settling the bill at the front counter one of the vets scurries out and whispers “we think your cat has fleas”. What just happened? We saw no direct evidence during the examination so how did we know later?

The answer is we find flea dirt as very small specks when we clean the exam table. The picture above shows an example where the amount was high enough to see in the coat but this is rarer. This is the best way to find fleas; by finding their poop! At home you can do this:

Recipe for finding flea dirt on a cat.

  • Get a clean light-coloured bedsheet
  • Bring magnifying glass, good light and spectacles
  • Get one hungry cat in the mood for cuddles
  • Place cat in centre of sheet
  • Give lots of pats, ruffles, belly scratches etc
  • Feed your cat so you can look at the sheet in peace
  • Search closely and collect any tiny black specks
  • Place specks on wet tissue and rub gently

How do you know it’s flea dirt and not just dust or soil? The proof is that flea dirt dissolves leaving a reddish brown smudge. After all, fleas eat blood, so although their poop looks black it’s actually dark red.

Now for the problem: most cats with fleas show no sign at all, not even flea dirt. I personally had a cat with a severe flea bite allergy on whom I never found one speck of flea dirt. OK smartypants, I hear you say, how can you be so sure? Because her skin problem responded magically to flea control every time, and every time I forgot it came right back.

We see this a lot. The fact that untreated dogs and cats with flea bite allergy almost always suffer tells us fleas are everywhere. If the companies selling flea control stopped fighting each other and spent the time educating the public about how pets catch fleas, they’d all be better off.

The truth is that flea eggs are everywhere: from stray cats in your garden, from other dogs in the street and at parks, etc. You can’t stop fleas jumping on your pet unless they live in a glass box.

If you want to know about the options for flea control for cats, visit Flea Control For Cats.

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.