If it is secondary infection at the wound caused by parasites, bacteria and fungi, it will cause edema in dogs. The pus needs to be cleaned up and treated with anti-inflammatories/antibiotics to control secondary infection.
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How to treat edema in dogs

Acute edema is mostly caused by allergies and requires desensitization treatment. The source of the allergy needs to be determined first through skin/blood testing and can be treated with antihistamines, steroids, antibiotic ointments and a special diet.