Angioedema is a similar disorder to urticaria, also known as hives. The bumps and bulges from angioedema are found in the subcutaneous level, in the fatty layer just below the skin itself, and  may or may not occur concurrently with hives. Although some of the subcutaneous inflammations are painless, others are accompanied by severe burning and itching sensations. Angioedema tends to cluster around the face area but can occur in any subcutaneous surface in the body. It can become dangerous if the swelling moves to the throat area and progression to anaphylactic shock is also possible.

Angioedema, a subcutaneous disorder, is a common skin reaction to allergens that produces red, raised bumps in the fatty layer under the skin that cause swelling and discomfort.

Angioedema tends to form on the face first, particularly around the mouth and eyes. When angioedema is caused by allergies, the reactions are usually swift. The characteristic bumps and swelling that occur under the skin usually form rapidly after the allergen is encountered, sometimes taking an hour or two to develop, and in other cases just a few minutes. Angioedema swellings sometimes produce itching and burning sensations like hives do, but these swellings can occur painlessly as well. 

Angioedema is not the only condition to cause cutaneous or subcutaneous bumps that can be indicative of an allergic reaction: 

Although any allergy can result in an episode of angioedema, certain types of allergens are prone to causing them. The most common sources for hives can include:

Certain breeds such as Bull Terrier, Boxer, and French Bulldog are somewhat over-represented in developing this allergic reaction.

Angioedema usually presents as a severely swollen face, although it can spread to any part of the body. Allergies are the most frequent cause of angioedema, but it can also be due to some illnesses and infections, like lupus and leukemia. The veterinarian is likely to request a biochemistry profile and a complete blood count which can rule out other disorders and may expose a type of white blood cell that would indicate an allergic reaction called eosinophils. Skin samples will often be taken from any areas that are affected by the swelling or by other types of rash, for use in the microscopic examination of the skin cells to look for issues like signs of disease, mites, or yeast infections. This type of evaluation is called a cutaneous cytology. 

Once it is determined to be an allergic reaction, the focus of diagnosis moves on to determining the allergen responsible for the result. In some cases, small amounts of the suspected allergen or allergens are injected under the skin to confirm that suspicion. In the event that the allergy is a food related allergy, dietary trials are often the best method to uncover which ingredient the patient is reacting to.

If your dog has developed angioedema due to an allergic reaction, your veterinarian will give you instructions on how to ease the itching and swelling or will recommend that you visit the clinic for further evaluation. Quite often angioedema disappears spontaneously, but it is important to monitor your pet's progress carefully to ensure that it doesn’t progress to a life-threatening condition. In cases where the severe inflammation persists, antihistamines like Benadryl or Zyrtec are often the first line of defense when it comes to treatments used to combat allergic reactions if medication is required. 

A veterinary professional should be consulted before using any over-the-counter medications, as the dosage for canines is quite a bit different than the dosage for humans, and it can vary based not only on your dog’s weight but also based on their physical condition and which other medications they may be taking. Antihistamines are only effectual in around 20% - 30% of dogs who are allergic and even those effects can fade with time, so in severe or chronic episodes steroids and corticosteroids may be required to alleviate the discomfort.

As allergic reactions tend to get more aggressive over time, it may be recommended that you get a prescription for an epi-pen if your dog has had a moderate to severe allergic reaction involving hives or angioedema. This device has a properly measured dose of epinephrine for your dog. Regular adult EpiPens are appropriate for canines over 45 pounds, and canines between 20-45 pounds will usually use the EpiPenJr, and animals smaller than 20 pounds will usually be given a syringe with the right sized dose for their size. Use of an EpiPen should be followed by a trip to the emergency room, even if your dog appears fully recovered. Epinephrine is a short-acting drug, and the allergic reaction may resume without proper medical treatment.