Merck Manual

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Pet Owner Version

Hives and Rashes (Urticaria) in Cats


Stephen D. White

, DVM, DACVD, University of California, Davis

Reviewed/Revised Aug 2018 | Modified Oct 2022

Hives or skin rashes (urticaria) are small patches of red, swollen, usually itchy, skin. They are very rare in cats and are most often associated with insect bites or stings or with medications. Hives may develop after inhaling, touching, or consuming allergens. When hives occur with severe swelling and fluid accumulation in other parts of the body (usually the head, legs, respiratory tract, or genitals), the allergic reaction can be life threatening.

The wheals (eruptions) appear within a few minutes or hours of exposure to the causative agent. In severe cases, the skin eruptions are preceded by fever, poor appetite, or dullness. They can develop on any part of the body but occur mainly on the back, flanks, neck, eyelids, and legs. In advanced cases, they may be found on the mucous membranes of the mouth, nose, lining of the eyes, rectum, and vagina.

Often, hives disappear as rapidly as they arise, usually within a few hours. Treatment may not be required. When needed, treatment may include rapid-acting corticosteroids. Hives may return rapidly if exposure to the cause is not eliminated. If hives are chronic, food or environmental allergens should be considered as potential causes. Death rarely occurs and is usually associated with swelling of the lining of the respiratory tract or anaphylaxis (a severe allergic reaction).

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