send someone away with a flea in their ear

Examples from literature

'I wonder,' he went on, after a brief silence, 'how it is there are no fleas here? 
Do you notice any trace of fleas? 
It is a fine thing to be a flea on a lion. 
Now, the long fur heated and worried the dog constantly and the fleas nearly drove him mad. 

flea | American Dictionary

flea
noun[ C ]
us/fli/
a very small jumping insect without wings that feeds on the blood of animals and people

Examples of flea

flea
Other mechanisms of spread were considered possible but less important than fleas.
Vibrations caused by human movement liberate adult fleas from pupae hidden in cracks leading to attacks by hungry fleas.
After treatment with insecticide to remove fleas, 9 or 10 rabbits were housed in each pen.
The effect of host density on ectoparasite distribution: an example of a rodent parasitized by fleas.
There was a preponderance of female fleas available during the first days of emergence from a batch of cocoons.
The fleas, after a few minutes, will be found dead at the bottom of the receptacle or among the hairs and feathers.
A certain number of fleas will probably emerge at once from it; but there will be many larvae and pupae still in the nest.
We found no positive association between infection rates and the presence of ectoparasites (fleas or ticks).
In the rat-trypanosome there occurs a contaminative infection through the dejecta of the fleas or lice which attack a fresh host.
Although male and female rabbits are infested from an early age, female fleas are reproductively adapted to the hormonal profile of the blood of breeding female rabbits [33, 34].
The weekly count of eggs and larvae from each experimental cage was divided by the number of female fleas, introduced initially or subsequently counted in the nest.
If fleas had reproductive equipment analogous to that of human beings, was it not obvious that the origin of fleas was not inanimate matter, but other fleas?
When they took it home in the car, they noticed that it was bleeding from its rear end, and was covered in fleas.
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