What are hives in dogs?
Hives, also known as urticaria, are a common skin condition in dogs characterized by raised, swollen, itchy welts on the skin that appear and fade quickly (within 24 hours). Hives develop when the dog’s immune system releases histamine in response to an allergen or other trigger. This causes fluid to leak from tiny blood vessels into the skin, leading to the raised welts.
Hives can appear anywhere on the dog’s body, including the face, ears, chest, abdomen, legs and paws. They may range in size from a few millimeters to several centimeters across. Hives are often round or oval-shaped. The welts themselves are typically pale pink or red in color and blanch when pressed. The surrounding skin may have a normal appearance or be reddened.
Common causes of hives in dogs include allergies to foods, medications or insect bites/stings, as well as infections and other diseases. Hives are not contagious between dogs or people.
What causes hives in dogs?
Hives in dogs are often caused by allergic reactions. The dog’s immune system overreacts to an allergen, releasing histamine and other chemicals that cause swelling and itching of the skin. Common allergy triggers include pollen, dust mites, certain foods, insect bites or stings, and medications.
Insect bites from fleas, mosquitoes, bees, wasps, and ants can also cause hives in dogs. The proteins in the insect’s saliva provoke an allergy response when injected under the skin.
Medications are another common cause of hives in dogs. Antibiotics, anti-seizure drugs, vaccines, topical spot-on flea and tick treatments, and NSAIDs like Rimadyl are among the drugs that may trigger an adverse reaction.
Bacterial, viral, and fungal infections can also lead to hives in dogs as a hypersensitivity response. This includes skin infections, ear infections, bladder infections, and upper respiratory infections.
Finally, autoimmune disorders like lupus and pemphigus foliaceus cause recurrent hives in dogs. With autoimmune disease, the immune system mistakenly attacks the body’s own healthy tissues.
How long for hives to appear after exposure?
Hives, also known as urticaria, is an itchy rash that can appear on a dog’s skin within minutes to hours after exposure to an allergen or other trigger. However, the appearance of hives can sometimes be delayed for up to a few days after the initial exposure.
In most cases, hives tend to develop rather quickly after contact with a potential allergen. The rash and itching usually starts within minutes to several hours. Common causes include food allergies, medications, insect bites/stings, and exposure to environmental allergens. With food allergies in particular, hives often begin to pop up within minutes to 2 hours after a dog has eaten the offending food.
However, hives can also sometimes have a delayed reaction time of a few days after exposure to the allergen or trigger. This is more likely with environmental allergens or infections. For example, some dogs may not react to a new shampoo or grooming product until a day or two later.
In summary, while hives often appear quickly, the timeframe can vary. Owners should watch for hives within the first few hours after exposure to a potential trigger. But delayed reactions are also possible, so continue monitoring the dog’s skin over the next several days as well if hives are suspected.
Acute vs. Chronic Hives
Hives can be categorized as either acute or chronic based on their duration:
Acute Hives: Acute hives, also known as acute urticaria, refers to hives that develop suddenly and last for less than 6 weeks. They often appear within minutes or hours after exposure to an allergen and may last from a few hours to a several days before fading. Acute hives are commonly caused by allergic reactions to foods, insect bites/stings, medications, infections, stress, or exposure to hot/cold temperatures.
Chronic Hives: Chronic hives, also known as chronic urticaria, refers to recurrent episodes of hives that persist for 6 weeks or longer. The exact cause is often unknown. Chronic hives may be triggered by food allergies, infections, immune system disorders, thyroid disease, or stress. The hives come and go over months or years. Getting to the root cause can be challenging.
The treatment approach depends on whether the hives are acute or chronic. Acute hives often resolve on their own, while chronic hives may require long-term treatment to control symptoms and prevent recurrences.
Mild vs. severe hives
Hives can range from mild to severe depending on the dog and the cause. Mild hives tend to be isolated, with just a few raised, red welts on the skin. The dog may show no signs of itching or discomfort. Severe hives are widespread, covering large areas of the dog’s body with raised welts. Intense itching is common, and swelling around the face or legs can sometimes occur as well. The more severe the reaction, the quicker veterinary attention is needed.
With mild hives, the dog can often be treated at home with cool water compresses and antihistamines. Severe hives may require steroids or other medications from the vet to reduce the reaction. It’s important to closely monitor dogs with hives and watch for any signs of increased swelling, difficulty breathing, or lethargy, which indicates a growing allergic reaction.
Diagnosing the Cause
When a dog develops hives, the first step is to take a detailed patient history to try to uncover potential causes or triggers. The vet will ask about the dog’s diet, any new foods, exposure to new environments, contact with new animals, flea/tick prevention, medications, and more. This can help identify any new exposures that align with the timing of the hives.
Allergy testing may also be recommended, most commonly intradermal skin testing. This helps identify specific allergens that could be provoking an allergic response. However, allergy testing is not always necessary if the trigger is obvious based on the history and physical exam.
It’s also important to rule out other conditions that can mimic hives, such as an infection, autoimmune disease, or mast cell tumor. The vet may recommend bloodwork, skin scrapings, biopsies, or other tests to confirm that hives are the correct diagnosis.
Treatment Options for Dog Hives
There are several approaches vets may take to treat hives in dogs depending on the severity and suspected cause:
Antihistamines – Antihistamine medications like diphenhydramine (Benadryl) can help counteract histamine release and reduce itching and swelling. They are often the first line of treatment for mild to moderate cases of acute hives.
Steroids – For more severe hive reactions, vets may prescribe steroid medications like prednisone to powerfully reduce inflammation and itching. Steroids need to be used cautiously to avoid side effects.
Immunotherapy – If hives are triggered by environmental allergens, allergy testing and immunotherapy injections can help desensitize the dog’s immune system over time.
Treating Underlying Causes – It’s important to try to determine what is causing the hives so that any underlying condition can be treated. This may include treating infections, managing endocrine disorders, changing diets, avoiding exposure to irritants, or managing anxiety/stress.
Treatment aims to both relieve current hive symptoms using medications while also addressing any underlying trigger to try to prevent recurrence. Most acute cases of hives can be managed at home, but chronic hives may require extended vet care.
Home Care for Dog Hives
If your dog develops mild hives at home, there are some steps you can take to help soothe their skin and reduce irritation:
Cool Baths
Giving your dog a bath with cool water can help soothe inflamed skin and provide relief from itching. Make sure the water is a comfortable temperature, not too cold.
Oatmeal Shampoo
Use a gentle oatmeal shampoo, which can help calm skin irritation and inflammation. Oatmeal contains natural anti-itch properties.
Prevent Scratching
Try to discourage your dog from scratching, licking or biting at their hives, as this can worsen the reaction. You may need to use an Elizabethan collar to prevent them from aggravating the area.
Avoid Triggers
If you suspect or know what the trigger was that caused the hives, take steps to avoid exposing your dog to that allergen again. This may mean switching dog foods, avoiding certain plants/pollens, or using flea & tick control.
When to see the vet
In most cases, mild hive reactions will resolve on their own within a day or two. However, some more severe reactions require veterinary attention:
Severe reactions: If your dog experiences rapid swelling of the face, ears, lips, eyelids, or tongue, this indicates anaphylaxis. This is a life-threatening reaction that requires immediate emergency veterinary care.
Persistent hives: If your dog’s hives last longer than 24-48 hours or seem to be getting worse, you should take your dog to the vet. The vet can provide medications to help control the reaction.
Lethargy, vomiting, etc: Some dogs may experience lethargy, vomiting, diarrhea or other signs of systemic illness along with hives. This indicates the body is reacting severely and needs veterinary attention.
Seeing the vet promptly can help get severe hive reactions under control. They can provide medications, guidance on avoiding triggers, and other care to help your dog recover safely.
Outlook and Prevention
The outlook for dogs with acute hives is generally good, as the condition often resolves once the underlying cause is identified and properly treated. Preventing future hives involves taking steps to avoid exposure to potential triggers.
For dogs with chronic idiopathic hives, the underlying cause can be difficult to pinpoint so the outlook is less straightforward. However, veterinarians can provide medications to help manage symptoms in the long-term. Preventative measures involve avoiding known allergens when possible and minimizing stress.
Some tips to help prevent hives in dogs include:
- Carefully introduce new foods, treats, and medications gradually to check for allergic reactions.
- Use flea and tick control medication as prescribed.
- Avoid letting your dog eat bees, ants or other insects that may sting or bite.
- Minimize exposure to pollen, grass, and other environmental allergens.
- Reduce stress from loud noises, travel, boarding, or changes in routine.
- Bathe dogs after potential exposure to allergens to wash off pollen, chemicals, etc.
While hives can be alarming to owners, the condition is typically manageable if the underlying cause can be found and addressed. Work closely with your veterinarian to determine if any allergen, infection, or condition is triggering the hives in your dog.
