26/09/2026
Hives and Rashes (Urticaria) in Dogs
Urticaria is generally an acute immune response (usually mediated by a type I hypersensitivity), often occurring within minutes of the stimulus.
Urticaria is the result of degranulation of mast cells and the subsequent release of histamine and other constituents into the dermis.Histamine release causes vasodilation and dermal edema.
CAUSE:
The specific cause is often not identified.Urticaria occurs most commonly as a result of an insect bite (eg, from bees, wasps, hornets, mosquitoes, black flies, ants, spiders, or certain caterpillars), drug reaction, vaccine reaction, adverse food reaction, or seasonal environmental allergens.
Additional causes of urticaria include the following:
-Inhaled or contact allergen
-Mast cell neoplasia
-Plants (such as stinging nettle)
-Transfusion reactions
-Viruses
-Bacteria
-Fungi
-Parasites
(Not all causes of urticaria are immunologic.)
Non-immunologic causes include the following:
-Heat or cold
-Exercise
-Pressure
-Psychological stress
-Histamine toxicosis (scombroid poisoning)
Clinical Signs;
-Urticaria may or may not be associated with pruritus.
-Common lesions in urticaria include acute-onset, haired, dome-shaped wheals.
-Dermal edema is often multifocal, leading to 0.5- to 3-cm-diameter wheals; however, it may be diffuse, affecting large areas of dermis or subcutis.
-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, re**um, and va**na.
-In severe cases, the skin eruptions are preceded by fever, poor appetite, or dullness.
Differentials:
-Folliculitis
-Neoplasia
-Bacterial cellulitis
-Sterile granulomatous dermatitis
-Lymphadenitis (juvenile cellulitis)
-Snakebite
Treatment:
-Urticaria may resolve spontaneously 12-48 hours after occurrence.
-Generally, urticaria and angioedema respond quickly to treatment with glucocorticoids and antihistamines.
-Urticaria may be a precursor to anaphylaxis.
-In some cases, urticaria may be chronic or require a skin biopsy.
-Death does not commonly occur, unless anaphylaxis (a severe allergic event) or swelling of the respiratory tract is present.
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