Cats have allergies too!

An allergy to flea saliva is the most common allergy we see in cats. Cats allergic to fleas groom more than normal and some develop large ulcers on their lips or in their mouths. Some scratch furiously around their head and ears, others develop pimple-like lesions on their rumps and trunks, or red lines on their legs and bellies. Cats are so fastidious with grooming that we frequently find no trace of the fleas.
After a thorough check for other parasites and problems we treat the affected cat, any other pets in the household and the house for fleas before we go on to allergies that are more difficult to treat and diagnose.
As usual cats love to confuse their vets - cats with food or pollen allergies may show all or any of the same signs as flea allergic cats! Food allergies are the least common type of allergy but we prick our ears up if a cat has intermittent vomiting or diarrhoea as well as skin signs. 
We prescribe a special low allergy diet if we suspect food allergy. If the signs go away on the diet then we trial different proteins until we find the one the cat is allergic too.
Atopy, which is the proper name for allergies to pollens, dust mites and other inhaled allergens, is more common than food allergy, but more difficult to diagnose and treat.

Herpesvirus for cats

Yes - cats have their own herpesvirus, just as irritating as the human variety, and liable to flare up with stress just like it does in human sufferers. However cat herpesvirus mostly affects the eyes and respiratory system.
The great majority of cats suffer their first bout with herpesvirus when they are kittens. They get watery eyes, sneeze, snuffle, go off their food for a day or two and look very sad and fluey. Antibiotics to prevent secondary infections and good nursing pull nearly all of them through.
Although most infected cats then become carriers very few have any further trouble with the virus themselves.
A few poor cats go on to develop flu-like signs or various eye diseases whenever they are stressed.
Some just get watery eyes. Painful ulcers on the cornea, the window of the eye, and on the conjunctiva, make other cats very miserable. Occasionally a part of the cornea dies and turns black, or the eye perforates.
Any eye problem is an emergency. If your cat has watery or pussy eyes, is squeezing his eyelids closed, or the eye looks blue, red or black bring him straight in to the surgery.