Allergic Reactions: Hives (Urticaria) and Swelling of the Face (Angioedema)
Veterinary & Aquatic Services Department, Drs. Foster & Smith

Hives (urticaria) and a swollen face (angioedema) are typical hypersensitivity (or allergic) reactions to drugs, chemicals, something eaten, or even sunlight.

What are the symptoms of hives and angioedema?

In hives, small bumps occur within the skin. Often, the hair will stand up over these swellings. Sometimes, they itch. In angioedema, we see swelling of the face, especially the muzzle and around the eyes. Sometimes, the swelling is so severe, the cat cannot open his eyes. Angioedema often results in itching. Facial swelling and hives generally develop within 20 minutes of being exposed to the allergen (substance to which the animal is allergic).

In general, these types of allergic reactions are not life-threatening and will go away by themselves. Rarely, the swelling in angioedema can affect the throat and make breathing difficult. A more severe allergic reaction, called anaphylaxis, is life-threatening, and requires immediate veterinary attention.

How are hives and a swollen face treated?

Antihistamines are generally the best treatment for angioedema and hives. If severe, steroids are sometimes given. If respiration is affected, epinephrine is administered. If your cat has hives or a swollen face, contact your veterinarian, who will advise you about the proper treatment.

Can hives and angioedema be prevented?

In general, there is no way to predict which animals may develop hives or angioedema as a result of exposure to a certain substance. If a cat has already had an allergic reaction, such as anaphylaxis, angioedema or hives, to a substance, the substance should be avoided. If your cat has ever had a reaction to a vaccine or medication, be sure your veterinarian knows and the information is placed in your cat's medical record.

If your cat has ever had an allergic reaction to a vaccine, subsequent vaccinations should be given by your veterinarian. Your veterinarian will probably administer an antihistamine prior to vaccination and have you remain in the office for 20-30 minutes after the vaccination, so you are right there if your pet has a reaction. In some cases, certain vaccines may be excluded from your cat's vaccination regimen, or a different type of vaccine will be used.

Many vaccines contain antibiotics as preservatives. If your cat is allergic to an antibiotic, be sure to check all vaccines for the presence of that antibiotic before use.

If your cat has developed hives or a swollen face from an insect bite, you may want to discuss various options with your veterinarian. Your veterinarian may give you a prescription for an 'epi-pen.' An 'epi-pen' is a special syringe and needle filled with a single dose of epinephrine. If your pet has an anaphylactic reaction or severe angioedema, inject the epinephrine using the 'epi-pen' and seek emergency veterinary assistance immediately. Be sure to take the 'epi-pen' with you on any trips.

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