By Dr. Stacy Matthews Branch, DVM
Seeing your dog suddenly covered in itchy red bumps is an all too common source of frustration for the dog and you as the pet parent. The first questions that come to mind are how to relieve your dog’s discomfort and suffering, why it happened, and how to prevent it from happening again. Some people have a good idea of the specific cause of their pet’s hives, but it is often difficult to know just what provoked the dog’s skin reaction in the first place. Urticaria, known by many people as hives, looks like raised, red, small bumps on the skin. You may just see the hair-covered bumps and your dog's desperate attempts to relieve the itching with biting and scratching. Understanding this skin reaction, the common causes, and the means to provide relief can reduce your and your dog’s stress.
Why does my dog have hives?
Hives are raised, itchy eruptions or welts that appear on the skin as a reaction to some substance or stimulus. Most dogs have hives due to some abrupt substance exposure or stress. Any healthy dog can experience hives; however, a dog may have a stronger than normal immune reaction to an exposure, making him more susceptible to developing hives. There are various causes of hives, and knowing your dog’s environment and activities can help better pinpoint the cause in your dog’s case.
What causes hives?
The most common, but not the only, cause of dog hives is an allergic reaction. This skin response occurs after there is a release of histamine in the skin. Histamine release causes blood vessel dilation and inflammation, which is seen as welts or wheals. When hives suddenly appear, there is usually a specific exposure that sets off a histamine release responsible for the biological changes leading to hives. Examples of exposures that can lead to acute allergic reactions are:
- Insect bites, stings, or swallowing an insect
- Plant materials
- Food allergies
- Vaccine injection
- Certain fabrics
- Chemicals in household products, on lawns, or even a pet product
- Environmental allergens (molds, smoke, and more)
- Dust mites
Although rare, hives can occur after strenuous exercise, sun/heat exposure, or stress. It is also not unheard of for a dog to develop hives due to an intestinal parasite infestation such as Giardia (1). Sometimes a good deal of investigative work is necessary to identify the cause of hives.
What are the signs of hives?
The most tell-tale sign of hives on a dog is the sudden appearance of small bumps on the skin. On hairless parts of the skin, such as the lower part of the abdomen or inner thighs, you may see round, raised, red bumps. However, you may only see round, raised areas of hair over the bumps, or you may just feel them when petting your dog. It is not uncommon to see larger swollen areas of the skin that are actually areas of edema, termed angioedema. In the case of angioedema, the swelling occurs at a deep layer of the affected skin and is often seen when the face or mouth is affected.
The bumps, or wheals, are often accompanied by itchiness, as seen by your dog scratching or biting the skin more often than usual. Depending on where the discomfort is felt on the dog’s body, your dog may scratch with her feet, rub the body against furniture or other objects, or even scoot. The scooting can be tricky and mistaken for full or irritated anal sacs. Although some dogs lie down and rub their backs and heads on the ground due to an attractive scent on the ground, some may do this to relieve an annoying itch. A dog with hives may also whine, pant, and shake her head due to the discomfort caused by hives. A dog with hives resulting from an allergic reaction may also have facial swelling, including around the dog’s eyes. Drooling can signal discomfort felt inside the mouth, as is often seen when a dog swallows a bee or is stung in the face by one.
Severe allergic reactions, or anaphylaxis, involve effects on the circulatory and respiratory systems. These rare reactions typically cause wheezing and difficult breathing, and the dog may become weak or collapse due to the contraction of the blood vessels and the limited blood flow that results. Prompt emergency medical treatment is required for life-threatening anaphylactic reactions.
How are hives diagnosed?
The veterinarian can diagnose hives when seeing the characteristic signs at the time of visit. Results of the physical examination and the information you provide regarding the dog’s diet, activity history, and any products you fed or used on your dog can help determine if the skin signs/bumps are in fact allergy-related hives or a distinct underlying condition. Diagnostic tests may be necessary, including a skin scraping for microscopic analysis. In some cases, blood tests would be beneficial and can allow assessment of the dog’s systemic health and levels of various types of blood cells. If it is suspected that your dog has hives due to an allergen, allergy testing is an option to possibly identify it so that you will be able to make modifications in her diet or environment to reduce or eliminate exposure.
Are hives harmful to dogs?
While the actual hives alone are not dangerous if limited to the small itchy bumps that go no further than that, the scratching by the dog can lead to more involved dermatitis or possibly infection of the skin. The cause of the hives is also important. If hives result from an exposure that also leads to angioedema along the airways, this can lead to a more critical condition requiring emergency treatment. Fortunately, the majority of cases of hives resolve quickly and do not advance to more severe conditions.
Treatment and prevention of hives
There are measures you can do at home for uncomplicated hives until you can get to the veterinary office. Your veterinarian may recommend giving your dog an antihistamine such as Benadryl (diphenhydramine) or Zyrtec (cetirizine). The treatment at the veterinary office for acute hives is usually an antihistamine (eg., diphenhydramine) and corticosteroid (eg., dexamethasone) injections, which can provide rapid relief for dogs with hives. If your dog’s hives resolve at home, it’s still a good idea to let your family veterinarian know so that it becomes part of the record and used as data if another similar or other health event occurs.
To help sooth your dog’s skin as the hives resolve, give them a nice oatmeal shampoo bath for some much-needed relief. Supplements containing omega 3 fatty acids can also provide relief for pruritus (itchy skin). Studies in dogs treated with oils containing omega 3 demonstrated improvement in pruritus and overall hair coat condition (2). Other treatment approaches are necessary if the offending allergen cannot be avoided and your dog develops chronic skin allergies.
If the allergen responsible for your dog’s hives can be identified and it’s avoidable, eliminating the exposure would be the best way to prevent hives and other related allergic reactions. When hives are due to a vaccine reaction, your dog can be pre-treated with an antihistamine injection prior to vaccination. Supplements with ingredients such as spirulina can support immune system health and may help limit allergic reactions when allergens are encountered (3, 4). Your veterinarian can help walk you through the steps needed to usher your dog through recovery from hives and take measures to decrease the likelihood of another episode.
To read more about your dog’s health and wellness needs, visit the Native Pet blog.
- Williams LBA. Generalized cutaneous urticaria associated with Giardia infection in a five-month old puppy. Vet Parasitol Reg Stud Reports. 2021 Dec;26:100643.
- Logas D, Kunkle GA. Double-blinded Crossover Study with Marine Oil Supplementation Containing High-dose icosapentaenoic Acid for the Treatment of Canine Pruritic Skin Disease. Vet Dermatol. 1994 Sep;5(3):99-104.
- Yang H-N, Lee E-H, Kim H-M. Spirulina platensis inhibits anaphylactic reaction. Life Sciences. 1997;61(13):1237–1244.
- Kim H-M, Lee E-H, Cho H-H, Moon Y-H. Inhibitory effect of mast cell-mediated immediate-type allergic reactions in rats by Spirulina . Biochemical Pharmacology. 1998;55(7):1071–1076.