What if a dog has an allergic reaction to flea treatment?

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Though rare, dogs can be allergic to the flea medication designed to protect them from fleas. The risk increases when purchasing flea medication over the counter at your pet store rather than consulting your veterinarian for treatment.

Reactions can be as mild as a rash to as severe as seizures that can result in death, so if your dog has sensitive skin or medication sensitivity, consult your veterinarian before applying flea medication.


There are many types of over-the-counter flea medication, a liquid designed to be squirted onto the dog's skin between their shoulder blades. These medications range in quality and can be obtained from a pet store or your veterinarian. All contain pesticides, but the Environmental Protection Agency (EPA) has declared some worse than others. It recommends avoiding products with these ingredients: chlorpyrifos, dichlorvos, phosmet, naled, tetrachlorvinphos, diazinon, malathion, carbaryl and propoxur. Flea medication is also available in pill form from your veterinarian.


Because the EPA has received so many complaints about over-the-counter flea medication, it is working on stricter regulations. However, even with regulation, flea medications still contain pesticides, and your dog may have an allergic reaction. Symptoms include red, itchy skin, welts, burns, vomiting, excessive drooling and seizures. This can lead to neurological disorders and even death if not properly treated.

Proper Usage

Veterinarians suggest part of the problem can be improper usage of the medication. The medication is designed to be used only once per month, but since some products don't kill fleas already on the dog, owners may try to reapply. Instead, bathe your dog to remove fleas. Some owners also apply the liquid near the base of the tail or other areas accessible to the dog. Make sure the medication is in a place where your dog cannot lick it off.


If your dog has an allergic reaction to flea medication, promptly rinse off the liquid and contact your veterinarian. If the reaction is mild, rinse your dog with oatmeal shampoo and contact your veterinarian about an alternative medication. However, if your dog experiences a severe rash, vomiting or excessive drooling, there's not much you can do at home. Veterinary care is required.


There are pesticide-free alternatives to reducing fleas, such as eucalyptus spray, nematodes, lemon rinse and regular cleaning of your dog and house. To make eucalyptus spray, add 1/4 tsp eucalyptus oil to 236 to 295ml of water and spray on your house and dog. In addition, leave eucalyptus leaves underneath your carpet to control fleas in your house. To make lemon rinse, place a sliced lemon, including peel, in boiling water and soak overnight before applying the liquid to your dog.