History: Diesel presented with facial swelling redness and hives on his chest and abdomen. His owner stated that he was outside for approximately 1 hour, and noted the swelling after 30 minutes. Owner gave him a bath the he began rubbing his face. Diesel began developing hives on the car ride to the clinic. The family’s yard is small and in a residential area, and they are not aware of any toxins or abnormal items that he could have ingested. Diesel had had no recent changes in his diet, no flea products applied, and no vomiting. He has no history of allergies or any other medical issues. He is also current on vaccinations and takes a monthly heartworm preventative.
Exam: All of the abnormalities found were associated with Diesel’s skin. He had generalized red skin (erythema) which was most pronounced on his head/neck, and swelling (angiodema) which was primarily affecting his face. He was itchy (pruritic) and also had hives (urticaria). Otherwise Diesel appeared to be a normal Boston Terrier.
Diagnosis: Suspected allergic reaction
Treatment: Diesel was given an intravenous (IV) injection of Dexamethasone SP, a corticosteroid. He also received an intramuscular injection of Diphenhydramine (Benadryl), an antihistamine. The purpose of giving both of these medications is to immediately start to combat the inflammation that is causing the swelling and the itching, as well as prevent release future release of histamine and other inflammatory mediators (these processes cause the allergic reaction). Diesel was kept in the ICU for approx 1 hour of observation. He was then released when we were confident that his facial swelling and redness had begun to improve and he was not having any difficulty breathing.
Discussion of allergic reactions: Allergic reactions can be a result of exposure and hypersensitivity to insect bites/stings, chemicals and medications (especially vaccinations), something eaten, etc.
What to watch for at home –
- Mild reactions: sluggishness/lethargy, short term loss of appetite, mild temperature elevation
- Moderate to severe reactions: Facial swelling is easily noted by owners. Signs include swelling and redness of facial skin, especially lips, muzzle, eyelids, and sometimes neck. Eyelid swelling can be so severe that animals can no longer open their eyes. Animals tend to be very itchy. These reactions may progress to anaphylactic reactions. Occasionally, it can even cause difficulty breathing which can be life threatening.
- Severe reactions – “Anaphylactic reactions”: Dogs may initially seem excited or anxious. Sometimes they will vomit and/or have a loose stool. Signs may progress to generalized hives, swelling, itching, pale gum color, high heart rate, etc. In some cases they can become depressed or even collapse. Some animals can develop severe respiratory problems and struggle to breathe. There is no particular order to which these signs appear.
Cats have very different reactions. They tend to develop difficulty breathing (respiratory distress.) Other signs they can develop include severe itching, vomiting, diarrhea, depression, and even sudden death.
Treatment: Depending on your pets’ signs and symptoms, your veterinarian will choose a course of treatments.
In less severe cases, a veterinarian may choose to administer antihistamines and/or steroids.
In more severe cases, such as anaphylaxis, hospitalization may be required with IV fluids, & medications. In patients with severe respiratory distress, intubation (placing a breathing tube through the patient’s mouth), and rarely a tracheostomy (breathing tube placed directly into the front of the throat) may be necessary to ensure that they can breathe.
Additional notes: Brachycephalic breeds (flat faced breeds, such as Pugs, Boston Terriers, Pekingese, Bulldogs, etc) are more prone to severe respiratory problems because they already have smaller airways that tend to develop more swelling. These patients should be seen by a veterinarian immediately for treatments and close observation at the first sign of an allergic reaction.
Anaphylactic reactions are VERY serious emergencies and can be fatal in minutes. If you suspect your pet is having this type of reaction you should take them to the nearest veterinary facility for immediate treatment.
If your pet has an allergic reaction within 72 hours of vaccinations, please inform your veterinarian (and any future veterinarians) of the reaction. They may wish to modify their vaccination protocol and/or keep him or her in the hospital for a period of time to watch for any reactions during future visits.