General Information about Allergies

Allergies cause reactions and unpleasant side effects caused by the cat’s immune system. The immune system helps a cat to build up resistance to viruses. Also, bacteria, foreign proteins and other irritating substances entering the system. In the allergic cat, certain foods, or substances such as pollen, powder, feathers, wool, house dust, and insect bites trigger a reaction. This is itching, and sometimes sneezing, coughing, swelling of the eyelids, tearing, or vomiting and diarrhea. For a cat to have an allergic reaction to something in his surroundings, exposure must occur to it at least twice. Allergen is the specific item that causes the allergy, such as pollen. Pollen is the allergen. The way in which his body responds to that allergen is a hypersensitivity reaction or allergic reaction.

There are two kinds of hypersensitivity reaction.

The immediate type occurs shortly after exposure and produces hives and itching. Hives in a cat cause sudden swelling of the head, usually around the eyes and mouth. Occasionally, welts appear elsewhere on the body. The delayed reaction produces itching which occurs hours or days afterward. Flea allergy dermatitis is an example of both types. Thus, this explains why a cat may continue to itch even after a successful flea treatment. Allergens, such as pollens or house dust enter the body in many ways. Some ways are the lungs, the digestive tract, by injection and finally, by direct absorption through the skin. While the target entry into the system in humans is the lungs, in cats, it is the skin or gastrointestinal tract.

Food Allergy

Cats may develop allergies to certain foods or even substances in their foods. Fish, cheese and milk are the most common allergens. An intensely itchy skin often develops. The reactions can include sneezing, swelling of the eyelids, and a runny nose. This reaction usually leads to diagnoses of Rhinotracheitis, Calici or upper-respiratory distress. In time, there will be hair loss and oozing sores from constant scratching. In about half the cases a food allergy produces profuse diarrhea. To make a diagnosis the vet exposes the cat to different suspected allergens, watching for a reaction. Treatment is to remove that allergen from the cat’s environment.

Flea Allergy Dermatitis

This skin disease, also called military dermatitis, caused by an allergy to flea saliva.  At one time, Veterinarian’s believed to be due to a food allergy, a hormone disorder or specific nutritional deficiencies. The affected cat breaks out along the back and around the neck with small crusts and bumps about the size of a small seed. These are the spots where fleas are most common. As the cat licks and scratches frantically, it sometimes produces patches of skin which become infected. Ulcers from licking may occur. Miliary dermatitis is the most common seasonal allergy of cats.  Most symptoms happen in the middle of the summer.  Yet, once the cat has sensitivity, if there are fleas around, the cat may have symptoms year-round.  Fleas cannot live about 5000 feet.  As result, there are no fleas at high elevations. Once the rash and fleas are found on a cat, the diagnosis is easy. To check your cat for fleas stand him on a sheet of white paper or paper towels and ruff up the fur. If there are black and sometimes white specs, those are flea eggs and flea feces. Spray the paper or towel lightly with water and you may see pink puddles form around the specs. Photo of cat with skin allergies


Kill the fleas by using one of the many safe topical or ingestible flea killers that your veterinarian recommends. Treat the premises with a hormonal treatment that sterilizes fleas and eggs. Vacuum daily to remove all traces of both fleas and eggs. This is a hypersensitivity of both immediate and delayed type. Both will persist a while after the fleas are gone. Your veterinarian may be able to prescribe something for the itching which should stop the scratching also.

Irritant Contact and Allergic Contact Dermatitis

Irritant contact Dermatitis and allergic contact dermatitis are two different conditions. We discuss them together because they produce similar reactions. Both caused by contact with a chemical. Any cat can contact an irritating chemical and develop a skin reaction. In some cases, only cats allergic will show an allergic skin response. A cat with allergies to certain chemicals will break out with contact dermatitis once exposed at least twice. Both irritant and allergic contact dermatitis affect parts of the body where hair is thin or absent. That is, the feet, chin, nose, abdomen, and groin. Also, these areas are the most likely to contact chemicals. Either type of contact dermatitis produces red, itchy bumps along with inflammation of the skin. Excessive scratching causes skin injury and infected sores. The rash of an allergic contact dermatitis may spread beyond the area of contact.

Chemicals producing irritant dermatitis are:

  • Acids
  • Alkalis
  • Detergents
  • Solvents
  • Soaps
  • Petroleum by-products

Common substances that produce allergic dermatitis are:

  • Flea collars and powders
  • Shampoos
  • Poison Ivy/Poison Oak
  • Plastic/Rubber dishes
  • Dyes found in carpets
  • Neomycin in some topical medications
  • Some kitty litters


Try to consider the area of exposure and look for anything your cat may contact that touches that area.  Then keep your cat away from it.  If it is plastic bowls switch to stainless steel.  If it is litter try different brands.  Remove flea collars at first sign of skin irritation.  Better yet do not use a flea collar at all and try a safe topical your veterinarian recommends. Cortisone is of some value because it stops itching and biting.  Discuss its use with your veterinarian. LSL Protection Status


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