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Occurring mostly during the hot summer months in warmer climates, mosquito bite hypersensitivity is a moderately common disease in cats.

It is an intense overreaction of a cat’s immune system to the saliva from a mosquito bite.

Signs and Symptoms

Lesions such as scaling and areas of crusts and raw ulcers on the nose or ears are a few of the more common signs of mosquito bite hypersensitivity in a cat.

Hair loss and colour pigment changes around the bite may develop in the long run on cats that have mosquito bite hypersensitivity.


Mosquito bite hypersensitivity is usually diagnosed by a qualified veterinarian.  Since it can also look a lot like many other types of skin disorders and allergies, it is important to rule out a food allergy, ringworm, eosinophilic plaque, lupus erythematosus, squamous cell carcinoma, or simply a bacterial infection.

Other factors that are considered before a diagnosis is given are the season of the year, the signs and symptoms, and whether or not the skin lesions had improved after a cat had been placed in a mosquito-free area for around 4 to 7 days.  Sometimes a skin biopsy is needed to confirm the diagnosis.


In most mild cases of mosquito bite hypersensitivity in cats, the lesions will resolve in their own time provided the cat is kept away from mosquitoes. It is encouraged that a cat remain inside the house during the recovery period.

Those cases that are more severe, however, may be treated with a corticosteroid to shut the allergy down.


Mosquito bite hypersensitivity can easily be prevented by limiting a cat’s access to mosquito prone areas.  Therefore, it makes sense that cats should not be exposed to mosquitoes by keeping your cat inside, especially during early morning hours and during dusk, because those are times when mosquitoes are most active.

If you feel strongly that your cat should go outside and enjoy the fresh air once in awhile, you could purchase what is known as a cat tunnel or outdoor cat run.  These are large, long, mesh enclosures that cats can wander through and also lounge in during the day. These should prevent the entrance of mosquitoes, depending upon the size of the mesh.

You can use mosquito repellants outside your house, such as mozzie-zappers.   BUT….please DO NOT apply human mosquito repellents to cats, as they groom the product off themselves and they are highly sensitive to the chemicals.