The signs of an allergic reaction in a cat are often relatively easy to spot. The most common is frequent scratching, as a result of a flea allergy. Other signs that may indicate an allergic reaction could include digestive complications, such as diarrhea or vomiting, labored breathing, constant licking or scratching near the hindquarters, and skin irritations. It is important to keep a close eye on a cat that may to be suffering from an allergic reaction in order to determine what kind of symptoms the cat is experiencing, and for how long. Concerned owners may wish to visit a veterinarian if symptoms appear to be severe or chronic.
Even a lone flea can trigger an allergic reaction in a cat, despite its owner's best efforts to ensure the pet is kept flea free. Hypersensitivity to flea bites may cause a cat to bite, gnaw, and scratch itself a great deal, particularly on the lower back and near the tail. This may cause hair loss and should not be confused with alopecia caused by an allergic reaction, although minimal thinning of fur in the problem area is possible due to a flea allergy. Other indications of dermatitis caused by fleas may include scabs and red bumps, or papules.
Food allergies in cats may not be the result of a change in diet. It is far more possible that a cat will develop an allergic reaction to food it has consumed regularly, so owners should not rule out food allergies when a cat is thought to be having allergic reactions. Common symptoms of a food allergy may include ear swelling or irritation, vomiting or diarrhea, and frequent itching on the upper portion of the cat's body, including the neck, head, ears, and face.
Other factors in a cat's environment can also cause allergies, including those things that typically cause allergies in humans, such as pollen, mold, or dust mites. Symptoms of an allergic reaction in a cat that is caused by an inhalant may include crusting lesions on the face, hair loss, and a skin rash on the back, neck, and head, which may be miliary dermatitis, a disease complex commonly associated with cat allergies. This kind of allergic reaction in a cat frequently starts during its youth, possibly becoming more severe as the cat ages.