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Dog has swollen marks despite flea prevention. What are they and how to heal?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Female | unspayed | 1 year and 5 months old | 15 lbs

Our dog is on a heart worm flea preventive combo and our vet said it would be a few months before she'd be flea free. Just noticed a few marks that have swollen. Going to call the vet in the morning, but just worried what they are and how to heal them.

2 Answers

Most Helpful Answer

Answered By Ricardo Fernandez, DVM

Veterinarian, Veterinary Oncology Resident

Published on September 14th, 2017

Thanks for using Petco Pet Education Center, formerly Petcoach! These skin lesions are likely pyoderma or superficial bacterial infection. Your veterinarian can prescribe an antibiotic and a medicated shampoo to treat them. The main thing is checking to see if there is any indication that she still have some evidence of fleas that could be causing these secondary bacterial infections in which case your veterinarian could consider something like Capstar to get rid of as many fleas as possible at once. Good thing is that these lesions are likely to resolve uneventfully. Good luck!

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Dr. Elizabeth
Veterinarian
Published on September 25th, 2019
That looks more like a skin infection than a laceration but I suppose an abrasion is possible. For a wound like this, you may cleanse it once a day with a baby wipe. After it is dry, you can apply a dab or organic coconut oil and rub it in well twice a day (don't get it in her eyes or ears). If it doesn't start getting much better in a week, have her examined by the veterinarian.
Regarding the fleas, top products for dogs are oral products such as Simparica and Nexgard. Top products for cats are topicals such as Revolution and Cheristan. There is also an oral product called Comfortis that both dogs and cats can take. You will need to switch all the pets over to a good flea product. Make sure to discuss these products with your veterinarian first. These products are generally safe for all pets but there are some conditions which are contraindicated for the oral products.
Cleaning up and treating the house and yard will also help but it will not clear all the fleas. The main control is making sure the pets are on good products. This is what will ultimately stop the infestation. Also remember every female fleas lays about 50 eggs a day and it could take up to 6 months before the eggs hatch. Therefore, you will need to treat for at least 6 months. Best of luck and please feel free to post any additional questions.
1Pet Parents found this answer helpful

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