Dogs can experience allergic reactions just like humans do. Often these are low-grade, chronic problems such as a food or pollen allergy, but dogs can have severe or anaphylactic reactions too.
Any time your dog is having difficulty breathing, it is an emergency and she needs veterinary care immediately. For mild allergic reactions, diphenhydramine (Benadryl) may be appropriate.
Allergic reactions happen when your dog’s immune system overreacts to something that normally is not harmful. Toxicity, on the other hand, happens when your dog’s body is directly damaged by something harmful.
Many of the symptoms of toxicity and allergic reactions are the same, so it can be difficult to tell the exact cause of the symptoms.
If there is any chance that your dog consumed or came in contact with something toxic before she started showing her symptoms, contact your veterinarian or a pet poison hotline. Both of these services are superb:
Pet Poison Helpline (855) 764-7661
ASPCA Animal Poison Control Center (888) 426-4435
These hotlines do charge a fee, but it gives you access to experts who know all of the latest details about what things are toxic to our dogs and how they can best be treated.
How Do I Know if My Dog is Having an Allergic Reaction?
Recognizing allergic reactions in dogs depends on what the dog is reacting to. Plants, bugs, household cleaners, and other chemicals are common causes of dog allergic reactions, but food and medications can also cause a reaction.
Dog allergic reaction symptoms include:
- Red, irritated skin
- Hives
- Chronic itchiness
- Sudden increase in itchiness
- Itchy ears
- Chronic ear infections
- Runny eyes
- Runny nose
- Sneezing
- Swelling
- Difficulty breathing (severe)
- Vomiting (severe)
- Diarrhea (severe)
- Pale gums (severe)
- Abnormal heart rate or cardiac arrest (severe)
- Collapse (severe)
- Tremors (severe)
Severe allergic reactions can result in death.
Dogs who are allergic to something that they inhale from the environment or to a food item usually have generalized itchiness and skin irritation. Chronic ear infections are a classic sign of a dog with allergies. Even if your dog is being treated for allergies, she may have breakthrough reactions if she misses a dose of medication or if she gets a particularly big exposure. In most cases, these allergic reactions are not life threatening, but they can be annoying for both you and your dog.
When a Dog Allergic Reaction is an Emergency
A dog allergic reaction is an emergency if she has:
- Difficulty breathing
- Pale mucous membranes (gums)
- Vomiting and diarrhea
- Weakness or collapse
- An abnormal heart rate
- Severe swelling, especially if it does not respond to antihistamines
- Unconsciousness
If your dog has any of these symptoms, contact an emergency veterinarian immediately. Your dog will likely need intravenous medications to stabilize her condition and prevent or treat anaphylactic shock, as well as supportive care to restore hydration and keep her comfortable.
What Can I Give My Dog for an Allergic Reaction?
If this is your dog’s first allergic reaction, or if it is more severe than previous episodes, we strongly recommend seeking veterinary care. Most allergic reactions that start out mild stay mild, but they can progress rapidly and put your dog in danger.
Antihistamines such as diphenhydramine (Benadryl), loratadine (Claritin), and cetirizine (Zyrtec) are safe for most dogs to temporarily alleviate allergic reaction symptoms. Call your veterinarian to get the right dosage for your dog. Always check the ingredients before giving any over-the-counter medication to your dog—avoid combination meds that contain multiple active drugs and avoid anything that has the artificial sweetener xylitol in the inactive ingredients, as these can be extremely toxic to dogs.
Diphenhydramine is typically given every eight hours until symptoms resolve or you have been able to get your dog to the vet’s office. This medication is generally very safe for dogs, but it is still always best practice to speak to a veterinarian before giving it to be sure it is appropriate for your dog.
For bug bites and stings, you can ice the area of the bite to decrease circulation in the area and relieve some of the discomfort and itchiness.
For contact allergies to something like a new laundry detergent or a floor cleaner, a bath with a gentle shampoo or with Dawn dish soap may be helpful to get the offending substance off your dog’s skin.
If your dog has previously been diagnosed with allergies and is experiencing a flare-up of her chronic symptoms, treat according to your veterinarian’s instructions. If you are out of meds and can’t get to the vet right away, a bath with an oatmeal shampoo can help to soothe irritated skin.
Even if your dog responds to treatment at home, touch base with your veterinarian to let them know what happened. She may be able to help guide you in identifying the cause of the allergic reaction or come up with a plan to prevent future reactions.
Common Canine Allergens
Flea allergy dermatitis (FAD) is a common allergy in dogs. These unlucky canines experience sudden, severe itchiness when even a single flea bites them. Dogs suffering from FAD often have red, bumpy, irritated skin, especially on the hind end. They may also have hair loss from all of the scratching and inflammation. Thankfully, FAD is easy to manage—treat all pets in your household for fleas year-round so that your allergic dog doesn’t get exposed to stray fleas. And be sure to treat the dog with FAD with a product that repels or kills fleas on contact and does not require a bite.
Household cleaners and chemicals usually cause reactions on the part of your dog that comes into contact with them. For these cases, your dog might have signs of a reaction on her paws, muzzle, side, or belly. For example, if she has an allergic reaction after lying on a bed washed in a new detergent, the redness and irritation will appear on parts of her body that touched the bed. Dog allergic reaction bumps may be itchy or may just show up as raised skin. Symptoms of the allergic reaction will go away once the dog is no longer exposed to the trigger.
Wasp stings, spider bites, and other bug bites typically cause localized reaction symptoms, but these can range from mild to severe. For example, one of my dogs gets big welts any time she is bitten by a bug. This is not an emergency, but it is uncomfortable for her.
Spider bites and severe reactions to wasp stings can cause dramatic allergic reactions in dogs, with severe swelling, difficulty breathing, itchiness, and even shock. The swelling from bug bite reactions is usually located right around the bite, but severe reactions can cause swelling throughout the body.
Kate, thank you for sharing your knowledge on allergic reactions. As I read your article I was anticipating what you would reveal about topical flea/tick medications. My German Shepherd mix fur boy had what appeared to be a toxic response to this insecticide being placed on his skin, panting, dilated pupils, physical agitation, running around the house as if trying to get away from it. I used a wet soapy rag to wipe off all the liquid that had not been absorbed. I spent the night repeatedly checking his gums and heart rate. This was a very scary event. Perhaps another article on reactions to these meds would be helpful to others. Ingestible flea/tick meds give him diarrhea, so I do not give him any preventative medication but am diligent about monitoring him for these pests. Perhaps current information on natural preventions would be useful as well. Sue and Bailey