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What to Do If Your Dog Has Hives or Another Allergic Reaction

a brown dog lays outside in a patch of grass with its paw over its head

Dogs love to go outside and play, which does make them more prone to getting an allergic reaction. Your dog may come back inside with a swollen face, and that’s your first sign that your dog may have hives or another allergic reaction that you need to address. In case you find yourself in this sort of situation, it helps to learn what to do when your dog has hives or another allergic reaction. 

The outdoors not only has the potential to cause an allergic reaction, but can also lead to your pup sustaining minor injuries. That’s why you need to keep Fauna Care’s healing sprays at home, to give quick and effective care to your dog’s scrapes and cuts. 

This article covers:

  • What an allergic reaction looks like
  • Types of allergic reactions in dogs
  • What the treatments are for an allergic reaction
  • How to prevent your dog from having another reaction

Signs of an Allergic Reaction or Hives

First, what causes an allergic reaction? An allergic reaction is an extreme response generated by the immune system to address an unknown substance your dog has come into contact with. The reaction can be caused by medication, vaccinations, pollen, dust, and food, but the most common cause after being outdoors is a bee sting or insect bite.

What will an allergic reaction for your dog look like? You’ll be able to tell when you notice swelling of the eyelids and face. Your dog will be itching and pawing at its face. A reaction can occur immediately or within 48 hours of contact with the foreign substance. The reaction could be mild, but it could also be severe and life-threatening. Because of that, it is always best if you contact your veterinarian as soon as you notice signs of an allergic reaction. 

Dog outside standing and scratching its face with its paw
A dog’s allergic reaction will show itself in a number of ways. A common sign is scratching. The dog may be putting its paw up to its face and bite at its paws to satisfy the itch caused by the reaction. 

A mild reaction may go unnoticed by you. Localized redness and itchiness are common after a bee sting or insect bite. You dog may experience joint soreness, lethargy, and a possible mild fever after a vaccination. It’s when your dog shows a more advanced reaction that you need to visit the veterinarian. Advanced symptoms can include vomiting, facial swelling, itchiness, and hives or bumps all over the body.
If your dog shows signs of difficulty breathing, weakness, and collapsing, your dog may have a rare and severe allergic reaction called anaphylaxis. This severe reaction can be life-threatening, as it has the potential to impact major organ systems, such as the as the gastrointestinal tract, the circulatory system and the lungs. Therefore, your dog needs an immediate trip to the vet if they show these symptoms.

Types of Allergic Reactions

Knowing the types of allergic reactions your dog is having can help you determine how serious it is and how to prevent it in the future. Take a closer look at the symptoms your dog is showing, and think back to what your dog was doing when the reaction began. Remember symptoms can show immediately or after 48 hours, so you may have to do a deep dive into your memories to find the cause. 

Anaphylactic Reaction 

Anaphylactic reactions are the most lethal allergic reaction, for both dogs and humans. Fortunately, they are also the most rare type for dogs.We see this reaction in dogs when they are bitten by an insect of if they get injected with a vaccine that they are allergic to. Antibodies react to the foreign substance, causing blood pressure to drop and sending the body into shock. If the dog has already had an incident of an anaphylactic reaction, the owner may carry with them an epipen in case of future incidents. 

Small dog running through tall grass
An allergic reaction that started outside might be caused by pollen or dust. Another common cause of allergic reactions for dogs are insect bites and bee stings. 

Facial Swelling and Hives

The next severe reaction a dog can have is swelling of the throat or face. This can include the lips, eyelids, and ear flaps. Swelling occurs usually between 30 minutes to a few hours after contact with the foreign substance. Once you’ve noticed swelling on the face of your dog, this is actually a good sign as it means the dog has likely surpassed the time for a lethal reaction to occur. Meaning the dog’s life is likely not in danger. If left untreated, the swelling with subside in a day or two.

6 to 24 hours after exposure, another reaction you might see is hives. For short haired dogs, this will be easy to see. For long haired dogs, you will have a better chance of feeling the bumps. Hives cause irritation and will make the dog want to itch them excessively.  

Skin Allergies

A widespread reaction for dogs is allergic dermatitis. This is caused by one of three things: fleas, food allergies, and atopic (environmental) allergies. 

When caused by fleas, dermatitis is the easiest to treat. The dog is reacting to the saliva of fleas, and the best way to treat it is to kill the fleas. 

Atopic allergy is usually seasonal and can be caused by pollen, mold, fungus, and house dust. The itch can be anywhere, but you’ll likely see the majority of itching at the paws and ears. 

Food allergies have the same symptoms as the atopic allergy. It is caused by certain ingested ingredients such as chicken or corn. The cause for food allergies is numerous. It could be a genetic predisposition, or the allergy can develop when exposed to the same ingredients constantly. Rotating meals helps to prevent this. 


Once you go to the vet, you may be able to determine the cause of the allergic reaction, but that won’t influence the type of treatment necessary. Treatment will depend on the severeness of the allergic reaction. A mild reaction only needs an oral antihistamine for 48 to 72 hours. Your vet will be able to recommend the dose and type that’s appropriate for your dog. For more advanced allergic reactions there are other medications for your vet to recommend. The various types of medication can reduce swelling, give cardiovascular support, dilate the lower airways to help your dog breathe better, and help the body stop reacting to the allergen. Hospitalization may be recommended, especially if your dog is suffering from anaphylactic shock, which requires aggressive treatment. 

Preventing Future Reactions

Prevention is difficult when you don’t know what the cause was. If you believe pollen is the cause, unfortunately there’s little you can do to avoid it. If it was a type of food or medication, these should obviously be avoided. If you’re not sure which food is causing the reaction, cautiously conduct an experiment of elimination. Every food ingredient the dog is currently eating should be taken out of their diet and replaced with foods never eaten by the dog before. You’ll know if it worked if after feeding the dog this new meal exclusively for six weeks, the reaction has subsided. 

Small dog on porch with unknown item hanging out of its mouth
It may be a certain food causing the reaction. It might take some cautious experimentation to determine what that food is so you can eliminate it from your dog’s diet!

If you know what the cause of the reaction was, you can set up precautions so another reaction doesn’t occur. Insect bites and bee stings can be difficult to avoid, especially if your pup is active and walks without a leash. If it’s a big concern, monitor your dog closely while they are outdoors to make sure they don’t offend an insect’s nest. 
If a vaccine was the cause of the reaction, that doesn’t mean you should avoid future vaccinations altogether. Make sure to inform your vet so proper premedication can be given. Premedication works for a lot of dogs so that vaccinations give them no allergic reaction. Talk to your vet about what diseases your dog is most at risk of and how you can minimize the number of vaccines administered. 

If you know vaccines cause a reaction, avoid having your dog accept more than one vaccine at one. If multiple are due, talk with your vet and schedule to have individual vaccines administered at least two weeks apart from each other. This helps to minimize the amount of immune system stimulation at once. If vaccinations are a known cause of allergic reactions, avoid vaccine clinics as they may be unprepared for administering premedication with anti-inflammatory medication and observing your dog afterwards. 

Seeing the signs of an allergic reaction in your dog can make any owner fearful. If you have any concerns or suspicions of it being a serious reaction, do not hesitate to contact your veterinarian and have your dog looked over with professional eyes. It’s better to administer treatment earlier rather than later.

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