Patches of red, itchy skin that are confined to a small area are known as hives or skin rashes (urticaria). They are rarely found in dogs, and tend to appear and vanish unexpectedly. Majority of urticaria cases are a result of medication, insect bites, stings, and shampoos. Some cases could be caused or aggravated by touching poisonous plants and chemicals, sunlight, stress, exercise, genetic defects, friction, and heat. Allergens that are inhaled or eaten also cause hives.
Skin eruptions emerge soon after being exposed to the allergen, and in extreme cases, the skin rashes are preceded by dullness, fever, and loss of appetite. Though they can erupt on any body part, the most commonly affected areas are the legs, back, eyelids, neck and flanks. Extreme urticaria leads to eruptions in the nose, oral mucous membranes, eye lining, vagina and rectum.
Treating hives may be unnecessary as they usually vanish as fast as they appear. However, they may recur rapidly if there is repeated exposure to the causative agent. Effective treatment may consist of fast-acting corticosteroids. Chronic cases of hives may be due to food, chronic, or environmental allergens.